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Are Consumer Firewall/NAT Boxes Really Secure? 166

blate asks: "Consumer-grade Firewall/NAT devices, such as those from Linksys, Netgear, D-Link, etc., have become very popular as more and more users get broadband connections. I've been using a Linksys router at home for several years and have never had any security problems. But how secure are these devices, really? The firewall guru's I know argue that a NAT really doesn't give you much beyond security-by-obscurity. What are your experiences with this (have you ever been comprimized through such a device)? Would I be better off with a Linux/ipchains firewall?"
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Are Consumer Firewall/NAT Boxes Really Secure?

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  • by Mr. Darl McBride ( 704524 ) on Friday September 05, 2003 @10:31PM (#6885073)
    I don't know of anyone who's been compromised, however it's worth a reminder that most of these boxes actually run an OS of some sort. We've seen that even Linux (upon which many of the Netgear and Linksys products are based) has had its kernel network exploits -- no major OS has been completely free of security problems.

    It's true that Most of these units are flash upgradable, but consumer-level network gear's support lifecycle tends to be pretty damned short. It's quite likely that the company producing the hardware isn't going to be bothered to repair a product, even if it's proven to be as permeable as a sponge.

    My personal take would be that these units are great, so long as you learn a little about how they work. Shoot for something that's based on Linux or another OS with public information, learn what kernel it's using, and then treat the unit just like a PC running that same release. If an exploit is announced for that version of Linux, get it off the wire until you can patch it, just like you'd do with the real PC.

    • by uradu ( 10768 ) on Friday September 05, 2003 @11:47PM (#6885435)
      > It's quite likely that the company producing the hardware
      > isn't going to be bothered to repair a product

      Now that's a platitude if ever I've seen one. What precise personal experience do you base this statement on? Linksys, Netgear and SMC certainly have a decent track record of supporting their products, sometimes well into the next few generations. Besides, most of these consumer devices are based on OEM hardware whose manufacturer usually writes the base firmware that the vendors then customize. The upshot is that even if your Linksys or SMC doesn't produce new firmware, the OEM manufacturer often does. My SMC 7004 Barricade is running firmware that provides considerably more functionality than SMC ever planned for the little box.
      • How do you find out what the OEM is? I have a 7401BRA barricade adsl router and would love to see what else there is for it :)
        • Don't know about the 7401BRA, but my 7004BR was OEM'ed by Amit in Taiwan. Products from Asante, 3Com and GVC used the same base hardware, and their firmware is interchangeable. You'll just have to do some googe grouping to find out.
      • Intriguing. What sort of alternative firmware exists for the SMC products? Got any resource recommendations? Search term suggestions?
      • Although I haven't actually tried one myself yet (although I plan on ordering one later today), the SnapGear firewalls seem to be the most serious protection you can get at a really low price.

        They're embedded Linux boxes, and SnapGear provides all upgrades for free, so there's no catch with having to have a maintenence contract as with some others.

        They seem pretty serious (much better than the average consumer gear, but not much more money), have a nice set of capablities, and are far more reasonably pric
        • > the SnapGear firewalls seem to be the most serious protection you can get at a really low price

          Just running NAT without a DMZ or port mapping alone gives you the single biggest protection all by itself. Everything else is incremental improvement above that. But for most consumers that don't know sh!t about security, the best and simplest advice is to just get a simple NAT box. Especially since such consumers are most likely to merely browse and use email and would be perfectly served by NAT.
    • "It's true that Most of these units are flash upgradable, but consumer-level network gear's support lifecycle tends to be pretty damned short."

      Not with Linksys, at least. The Firewall/NAT box I purchased four years ago (BEFSR11) is still being sold, and I still get firmware upgrades for it.
      • And it is probably a LOT cheaper now than when you got it.

        This isn't funny people, this is insightful. It really works and is good protection, under $50. If you don't have one, go get one. I recommend the BEFSR41 though because it has a built in 4 port 10/100 switch.
    • by goombah99 ( 560566 ) on Saturday September 06, 2003 @06:46PM (#6889801)
      As has been noted these routers are not plug and forget. YOu do need to apply patches . you need to know your new drivers will work with what ever version of OS and other software you are using. And frankly you need a freindly GUI interface so you know you aren't doing something stupid when you infrequently have to remember how to maintain your system.

      hence apple airports are well worth the $50 premium you pay for them. The Apple software update will come with patches as needed for your security. You dont need to go looking, your apple will automatically get them the the moment they become available. You just have to run them. And you can be sure the apple updates will work well and not screw up your otherwise stable system. And the maintinence of the system is a freindly gui.

  • um (Score:2, Informative)

    by Anonymous Coward
    The firewall guru's I know argue that a NAT really doesn't give you much beyond security-by-obscurity.

    Then your 'gurus' are dumbasses. Practially nothing gets past NAT. About the only thing that can compromise it is a trojan.

    Your linux box is far more prone to hack attacks than an embedded device.
    • Re:um (Score:2, Informative)

      Your linux box is far more prone to hack attacks than an embedded device.

      Half of the current embedded devices are Linux boxes. :) The only difference is that most script kiddies don't know how to rewrite flash memory, so you can undo the eventual compromise with a power cycle.

      Think of it as a little gateway box running Linux off CD, but without the ability to run intrusion detection software.

    • Re:um (Score:3, Informative)

      by Anonymous Coward
      Practially nothing gets past NAT

      You can create packets that a NAT will convieniently route to it translated LAN. We frequently see packets that are addressed to the 192.168.0.x range on the LAN. Really cool, especially given that folks seldom change the default address ranges. Kids, if you didn't know this, try it -- it's a good time!

      NetGear ProSafe firewalls are the better bet as they are true stateful packet inspection firewalls. Of course, with great power comes great responsibility.

      Firewall tips
      • by schon ( 31600 )
        You can create packets that a NAT will convieniently route to it translated LAN

        If so, then the 'security device' is broken - and has nothing to do with NAT.

        Always block/log SSH, Telnet, FTP, TFTP, HTTP

        Actually, you should block everything, except for stuff you know you need.

        Use a non-standard IP address range for your LAN

        Wrong - assume that anyone on the outside knows the IP address range you use for your LAN. Attempting to 'hide' this is security through obscurity - it does nothing to enhance yo
      • by phorm ( 591458 )
        Never allow PING

        Being allowed to ping your server is quite often convenient if you're having weird issues. Rather, you can restrict the addresses a PING is allowed from, or put in anti ping-flood rules (which is what I assume you are worried about).

        If your firewall is a NAT type, run a software firewall on your desktops

        The primary reason I love my NAT box is that ZoneAlarm and others also slow down my PC net connection, and cause other oddities.Having a proper NAT box means you shouldn't need anothe
    • by schon ( 31600 )
      Then your 'gurus' are dumbasses

      I wouldn't call them dumbasses, but they certainly haven't thought through it through.

      Typically, NAT can be thought of as "poor-man's stateful packet filtering". That is, it provides a method for your security device to track inbound and outbound connections.

      This is, of course, a very obvious security enhancement over standard packet filtering, and has nothing to do with obscurity.

      Now, if (as another poster said) that the devices don't filter properly, then that's a sepa
  • morph (Score:5, Insightful)

    by m0rph3us0 ( 549631 ) on Friday September 05, 2003 @10:36PM (#6885095)
    NAT generally is equivalent to a firewall that disallows incoming connections. Some consumer firewalls allow a DMZ (connections made to the firewall are forwarded to the DMZ box). If you need more advanced rules than that then you need something like Linux. Personally, for a free OS based firewall I would use OpenBSD, lots of cool features. However, if you don't need more than what the consumer firewall provides it is a very cheap solution. Just keep the firmware up to date and disable the external administration.
    • However, if you don't need more than what the consumer firewall provides it is a very cheap solution.

      It is true that OpenBSD systems may be more expensive in terms of TCO than a $50 home router, but only if your time has value. If you're a bored student with too much free time like me, you can get an OpenBSD router/firewall up and running literally for free, using old commodity hardware. I've used OpenBSD as a router on machines from a Pentium MMX 266MHz all the way down to a Pentium 60MHz, with no pro

      • Re:morph (Score:2, Insightful)

        by Lost2Home ( 674278 )
        It is true that OpenBSD systems may be more expensive in terms of TCO than a $50 home router, but only if your time has value.

        Or if you have to pay for electricity, or if space is limited.

        The big question is whether the consumer router lets you do what you want/need with your network. The Linux/OpenBSD solution gives you the ability to do a lot of things that would otherwise require commercial grade equipment.

    • port forwarding
      port triggering
      dynamic routing
      AOL parental controls f
  • by PD ( 9577 ) * <> on Friday September 05, 2003 @10:37PM (#6885103) Homepage Journal
    1) You've got to keep your firewalls up to date with the rest of your software

    2) Don't build a maginot line that a hacker can plow through and then discover that Paris has no more defenses. Good security is always a series of obstacles, as many obstacles that you can put in the way. Not one of them will be perfect, but enough obstacles that are sufficiently difficult will keep a hacker out. So use that Linksys router. And run a router on each box. And make sure that your subnet isn't routable or addressable from the outside. And make sure your external facing machines are firewalled from your internal network. And make sure that your patches are up to date. And scan your internal network often to make sure than no funny ports are open. And read the advisories. And run a virus scanner. And don't use Outlook for a mail client. And don't forget to use that nmap against your external network interface frequently; if that means getting an Earthlink account just for scanning your network from the outside then do it.
    • by PD ( 9577 ) *
      Duh, I made a mistake. Don't run a router on each box. Run a FIREWALL on each box. Ipchains or Iptables or whatever.
    • No, the Germans didn't go through the Maginot Line but the Eqyptions went through the Bar Lev Line is something like 12 hours. The point is still good.
    • To follow up on #2, a firewall at the top of your broadband connection is a great thing.

      But when that moron down in dials up to AOL or his favorite ISP from his office machine, your defenses have just been breeched. His insecure windows system is now like a hooker waiting for the navy to come in. Every port open and ready.

      So, yes, in addition to a strong firewall, be sure to regularly scan the internal network for problems.
  • IPCop (Score:5, Informative)

    by Anonymous Coward on Friday September 05, 2003 @10:39PM (#6885114)
    Get an older computer, two nic's and IPCop [], and you'll be good to go. It's a linux distro customized just for nat/firewall/proxy use, and it's easy even for a novice to setup. A more advancded user can, of course, customize it quite a bit. The latest version even supports traffic prioritization with just a tiny amount of work, and the next version will have a GUI for that.
    • Why get a Linux distro that's trying to be OpenBSD when
      you can get OpenBSD for the same price?
    • by Glasswire ( 302197 ) <> on Saturday September 06, 2003 @05:24PM (#6889389) Homepage

      1) if you're familiar with Linux it's easy

      2) Great web/SSH interface esp. to snort output

      3) Works really well

      4) Quick and easy to install -very flexible about DMZ configs

      5) Runs nicely on a box I'd need to upgrade (need +10GB HD) to put Astaro on it. (But I might do that at some point)

    • Having recently replaced the antique Linux box that functioned as our household router/NAT box for the past six years, I feel obligated to explain why it got replaced: for $40 plus tax, the new router/NAT consumer appliance uses 7.5W versus the 150W power supply, is completely silent versus the power supply in the old box that has always been fairly noisy, and occupies a few cubic inches next to the cable modem versus the cubic foot or better of the old desktop enclosure. On the down side, the appliance is
      • Should have bought a SMC router, many of them have print servers built into them. The new cheapie SMC's even have real SPI Firewalls in them doing more then just blocking all inbound packets. Sure it isn't a highend firewall, but they are really quite impressive for what your spending. I mean something that costs less than $50 and emails you if someone is trying to SYN scan or DOS you is pretty cool.

        If my 7004BR wasn't so dam reliable(been running for years with barely any reboots) I'd replace it for anoth
      • Re:IPCop (Score:5, Informative)

        by Awptimus Prime ( 695459 ) on Sunday September 07, 2003 @11:46PM (#6897188)
        I attempted to do the same thing a while back. I have an aging P2 400, 4 port ethernet card, and small HDD in the system. I figure it burns probably around 75-100 watts sitting there, plus it generates some noise.

        When Compusa had a sale on those silver netgear routers, I grabbed one for ~$50. It sounded so simple, just plug it in, configure via web interface and you are done.

        Then I tried to get it to work with SecuRemote VPN, and no luck. The box said in big, bold letters 'Supports VPN!'. So I dropped them an email and found they had shipped them without a VPN enabled firmware and I upgraded so it would work as advertised. The new firmware worked with my VPN client, but only one session at a time. Then it started hanging and not passing traffic every couple of hours. I'd have to reboot the thing several times a day. After reading on forums, I found the VPN firmware was buggy as all get out.

        So I take it back and grab an SMC. This worked flawlessly, then started requiring a daily reboot after a couple of weeks usage. There were no firmware revisions to swap out, so I took it back to the store.

        Since then, I hooked up my old P2 400 with IPCop and found it to be rock solid. It's been up for about 4 months without a reboot and, not once, have I had to trouble-shoot any problems with it.

        If you get paranoid, Snort is there and simple to use via the web interface. I would definitely suggest this distro to anyone who's a Linux noob. You can download the ISO, burn it, pop it in, answer it's questions and have a very stable router running in about 30 minutes.

        Yes, for security's sake OpenBSD would be a better choice, but this Linux distro will make setup much less painful. If you are concerned about security enough to point out the flaws of Linux and preach BSD, you don't need to be running this distribution anyway, as you are likely versed enough to set up your own BSD solution. In my case, I'm lazy and the ability to just grab security updates via a web interface fits my needs a bit better.

        • I have a Linksys. I love it. The only issues I do have is my Pocket PC's WiFi (two different manufacturers of PPC's had same problem) does not release the DHCP address properly (at least I think....). I occasionally run out of IP's. No big deal...web into the box and release the IP's. My WiFI router is not broadcasting SSID and I am using WEP and MAC address filtering and running a software firewall on the desktop. Not running on the laptop because I only occasionally connect with it and I have not go
        • Really, you don't even need a P2. I had a little P233MMX that worked fine (power consumption nominal, as was noise as it ran nicely with just a heatsink and no CPU fan).

          Ah, the days when you didn't need a heatsink the size of the eiffel tower and a fan capable of running a hovercraft... old machines do just fine for Routers/NAT and save power/noise/heat too.
  • by pillohead ( 553676 ) <> on Friday September 05, 2003 @10:40PM (#6885118) Journal
    You don't gain much by using a dedicated computer, just more complexity and knowledge. While you do get to customize and tweak a computer far more than the little firewall/nat routers you also run the risk of misconfiguring it and making it worse than no firewall at all.

    It all boils down to this, what you rather spend more of? Time or money? I use freebsd with natd/ipfw it's great for me, but I did it for the learning experience.

  • by Lacertus ( 171358 ) on Friday September 05, 2003 @10:40PM (#6885125)
    Back when I was still in High School, I was lucky enough to land a job as the network admin of a small business, consisting of about 30 people or so. The entire shop was Open Source/Free software because cost was a major concern and that was what I was most experienced in (I basically did everything from running the copper across the ceiling to building the [admittedly crappy] webpage).

    That being as it may, I was relatively inexperienced with ipTables, and honestly didn't know my ass from my forhead when it came to admin-ing. As such, I deployed one of the cheaper netgear firewalls; and to great success, I might add. Though it caused some isolated problems, it did its job and protected our network. Thus I can say I was happy with its performance.

    As I've progressed in my techy career, I moved from such 'off-the-shelf' solutions, to building my own (extensive) iptables ruleset, to actually engineering my own 'blackbox' devices - these self-engineered devices were a product of my more ingenious years in college.

    Well, this ramble can be summarized thus: "depends upon your application." Yes, Netgear et. al. produce a decent, well designed product. These solutions don't often attract much attention from the geek crowd due to their boilerplate nature, but they are function.

    Now maintaining a rather massive network of thousands of people, I put my trust in a standalone, (sometimes) load-balanced front end consisting of an old x86 box running OpenBSD. The ruleset I carry with me is the product of several years of gradual modification, and is the best solution available (IMO).
  • by BusterB ( 10791 ) on Friday September 05, 2003 @10:43PM (#6885147)
    Not to speak of security, but I have tried a couple of these small firewall boxes, a linksys and an SMC, up against Roadrunner's DHCP and SBC DSL's PPPoE connections. The biggest problems I had were that these boxes would drop connection big time if there was any kind of service ripple, and more often were unable to reconnect without restarting the box (power cycle or via the web interface). The SMC couldn't run for more than a couple of days over PPPoE without a reset.

    Both FreeBSD and Linux have proven to be much more reliable against sometimes quirky network conditions. My current machine will have a new IP address and have updated my entries within 30 seconds of plugging in my DSL modem.

    If you're going to get a firewall/router
    appliance, get one that has something like Linux or BSD at its core.
    • I up your negative anectode with a positive one. I'm running an ancient SMC 7004BR flashed with the latest OEM firmware with all sorts of goodies, and it's never let me down. There were a few weak firmware releases, but you just check the buzz on the relevant forums and avoid them. I have it on Comcast, and while they're generally quite stable around here, they do have periodic outages. The little box handles that quite gracefully and always comes back up nicely. I only ever have to reboot it when fiddling
  • NAT, meet Britney (Score:3, Insightful)

    by _iris ( 92554 ) on Friday September 05, 2003 @11:07PM (#6885261) Homepage
    These "gurus" you know aren't really gurus. It seems "security-by-obscurity" is the new network security buzzword. If something obscures some piece of information, then that is suddenly its goal.

    Think about this. If you did use ipchains, what would your first and most important rule be? My answer to that question is "deny all" (for a home network anyway). A side effect of NAT's inability to automatically map incoming connections is essentially a "deny all" rule. Because you probably need more than one IP address, you'll probably use NAT anyway. Therefore, you get this "deny all" rule for free. It, of course, doesn't hurt to use a linux-based firewall in addition to the NAT machine.

    To sum it up, I wouldn't worry too much about it. It's not like anyone really wants your porn anyway :]
    • To sum it up, I wouldn't worry too much about it. It's not like anyone really wants your porn anyway :]

      And you weren't bothered at all by the extra traffic generated by CodeRed or slammer?

      Network security is something that affects the entire network -- any compromized host is a bad thing. Worms can only work if there are vulnerable hosts waiting.

      I don't worry about Grandma's port collection being compromised... I worry that Grandma's machine will be hijacked to send out worms and spam.

      - Peter
      • > I worry that Grandma's machine will be hijacked to send out worms and spam.

        And again, how exactly is this a NAT vulnerability? After all, if you remember, that's what we're talking about here.
  • heh (Score:5, Interesting)

    by revmoo ( 652952 ) <slashdot.meep@ws> on Friday September 05, 2003 @11:32PM (#6885366) Homepage Journal
    I personally have found a couple of exploits in my linksys router. I talked to linksys about it, after about an hour with tech support they finally said "We don't have a fix for it, I've never heard about it, but I'll forward this to our developers.

    Which was the last I heard about it.

    Basically, the gist of the problem was that outsiders on the internet were able to access SMB shares through the router on the internal network even though the ports were not forwarded. Even null routing those ports didn't work.

    So, no, consumer NAT devices aren't really secure, but they are still an extra layer between you and "The world", which is nice if you run windows(I didn't need to worry about Blaster, or it's variants thanks to the linksys).
    • Re:heh (Score:4, Informative)

      by cicadia ( 231571 ) on Saturday September 06, 2003 @12:15AM (#6885533)
      Why would you call tech support about that sort of thing?

      Linksys has an email address, [mailto] set up so that you can report things like this. Tech support is for people who can't tell the LAN cable from the WAN cable, or need to be told to power-cycle their routers.

      And if you don't hear anything back for a while after emailing them there, try posting it to Bugtraq [] -- that'll get their attention, if nothing else.

      • Re:heh (Score:5, Funny)

        by Asprin ( 545477 ) <gsarnold@ya[ ].com ['hoo' in gap]> on Saturday September 06, 2003 @09:11AM (#6886784) Homepage Journal

        "...people who can't tell the LAN cable from the WAN cable..."

        The mental image I had on reading this was priceless - A dad sitting at home on the phone with a red RJ45 patch cable in one hand and a green RJ45 patch cable in the other.

        "So the WAN cable is

        Yeah, I know, it's early.

  • by TheLink ( 130905 ) on Friday September 05, 2003 @11:33PM (#6885372) Journal
    ipchains is stateless. iptables is ok.

    As for consumer NAT boxes? Well they're a lot harder to attack if they are done even half-baked. Coz NAT creates a fair number of barriers against inbound connections - an inbound packet needs to match an entry in the tables to go in to the right address/port pair behind. Unless there's a major screw up in the table matching bit, where is a packet going to go if there's no matching entry?

    Maybe if they cut a few corners with DNS packets then the attacker could try sending spoofed DNS packets to trick people to go to a custom webmail site. Thing is, an attacker needing to have a site means leaving a bigger trail and the site can usually be shut down.

    The usual holes in NAT are usually in handling NAT unfriendly protocols like FTP, H.323, IRC-DCC and so on. In fact if the box doesn't handle these its probably safer, so what if you lose a few features - Joe Schmoe doesn't even know about FTP, and really Joe Schmoe not being able to DCC files from someone (and stupidly run them) is a feature.

    The other potential vulns are DoS - crashing the box - exploiting a box could be harder if it uses microprocessors which the attacker can't be bothered to get access to and figure out (most are script kiddies).

    In all I think they are a good thing - such cheap firewalls significantly raise the barriers of entry to the masses.
  • by hbackert ( 45117 ) on Friday September 05, 2003 @11:37PM (#6885384) Homepage

    I never had any problems with off-the-shelf el-cheapo no-name home routers. I installed 4 such routers, 3 different brands in 3 companies and here at home. The latter one is a temporary solution, the other ones run for about 2 years now. No problems, except PPPoE related issues (MTU size limit and Linksys' inability to fragment them correctly, but this is an old Linksys). Even companies which wanted a more sophisticated router (Yamaha, Cisco) wanted: NAT, nothing incoming, everything outgoing. Not different from cheap home-routers.

    That said, while a NATing router might not be the worlds securest solution, it's a very simple one and a pretty effective one too as long as users don't use the 'DMZ' feature, but I don't know anyone using it without knowing what it does in terms of attackability. For the money you pay, you get the ability to connect more than one computer to the Internet, and they are all no longer easily attackable. Great value for money.

    Imagine a world where all users had those. Windows viruses/worms would have a much harder life to spread.

    The key here is, that it's cheap and easy to use and it actually works. Compare that with a far more complicated Linux/*BSD firewall solution.

    • by fm6 ( 162816 )
      I agree with you on every point, but one of your points needs further elaboration.

      It might seem strange that a cheap router could provide such high level of security. It's effective for the same reason that it's cheap: the technology is very simple. Machines on the local network can open connections to remote machines, but no remote machine can access a local machine. In fact, remote machines can't even address local machines -- the network IP addresses are meaningless outside the local network. This is f

  • My Experience (Score:4, Informative)

    by Ratbert42 ( 452340 ) on Friday September 05, 2003 @11:37PM (#6885387)
    I've run the following firewall/host setups:

    Linux (Redhat 6.1-ish?) firewall/occasional web and ftp server with a mix of Windows clients. The Linux machine was never compromised but it did begin crashing on a regular basis, I believe due to DoS attacks of an unknown form. I retired this box due to the crashes.

    OpenBSD (3.0?) replaced this box with the same client load. No problems and no compromises, but keeping up with patches, particularly rebuilding the kernel, was a pain on such a slow machine.

    Linksys box replaced that in the same environment. Again no compromises, but still no services really exposed. The lack of configurability compared to Linux/OpenBSD boxes was a pain.

    Current setup of 3 static IP's, 2 with Linksys boxes protecting web/dns servers and 1 with a DLink WAP/NAT firewall box protecting client boxes. The servers (1 OpenBSD 3.3 and 1 Windows 2000) have had no compromises and the Linksys boxes have given me no problems at all. The DLink box is a pain because it apparently drops idle tcp connections after about 5 minutes. It's much more configurable than the Linksys boxes though. Still no compromises through the DLink firewall either.

    So in short, I've never had a compromise through any firewall, hardware or unix-ish box. The only compromise I've had (except the DoS crashes on the Linux firewall) was a trojan from a downloaded piece of software.

  • by Zocalo ( 252965 ) on Friday September 05, 2003 @11:50PM (#6885445) Homepage
    Given that most devices on the market today come with firewalling included by default, you might as well use it! There's nothing to stop you putting a Linux/BSD based firewall behind it if you wanted too, and of course, you *do* have a personal firewall on each of the Internet connected PCs, right?

    I have a routed block at home, and my basic setup is to use the embedded firewall (it's BSD running IPF as far as I can tell) to perform basic ingress/egress firewalling, DoS and portscan detection etc. and provide an Internet synched NTP server. All the firewall rule violations get sent back to a Linux box via SysLog and I also monitor network devices via SNMP. *All* my internal kit is restricted access by a local firewall; IPTables on the Linux boxes and Agnitum's excellent Outpost Pro [] on the Windows boxes. On top of all that, I have a slew of other stuff; TCPWrappers, a NAT'd wireless network locked down by MAC address, my switch is also locked to MACs and there is a small battery of IDS stuff running.

    • That's the setup. How does it work? Very well it turns out; here are the stats for Friday:
    • IP sessions blocked by gateway firewall: 4072
    • IP sessions blocked by local firewalls: 0 (that's zero!)
    • Probes of FTP server: 1
    • Probes of HTTP server: 16 (looks like Nimda's nearly dead)
    • Probes of SMTP server: 0 (that's suprising!)
    • Probes of SSH server: 0 (ditto)
    So, yes, it does look like these things are very effective, if you set them up properly of course!
  • cheap test (Score:5, Informative)

    by DuctTape ( 101304 ) on Friday September 05, 2003 @11:58PM (#6885483)
    One cheap (i.e., no prep) test from the outside is to head over to Gibson Research's site [] and have it run the Shields UP scanner on your system (links at the bottom of the page). Probably rudimentary, but it'll tell you what you look like from the outside, with pretty pictures, too. It also tells you when your firewall probes them back.

    And of course, for the Windows users, there's our free friend Zone Alarm [] to help put another layer between your machine and the bad ol' Internet.


  • NAT Issues (Score:2, Informative)

    by jazman_777 ( 44742 )
    I think there's been some noise about ISPs being able to figure out you're NATting from the packet info. I think you can obscure that with OpenBSD. With the Linksys et al you can't. Who cares? When the ISP decides to charge per computer on your LAN...
    • Re:NAT Issues (Score:3, Insightful)

      by acidrain69 ( 632468 )
      I'd like to see them try. I do tech support for one of the larger DSL co's in the US, and I couldn't imagine the outcry if they started instituting that. The only damage having a NAT does to the ISP is for the people who don't know what they are doing who call up for help to setup the NAT/router. We only support the NAT's and routers that we sell, if they call up about a linksys or a netgear, we send them to those manufacturers.

      I remember the noise about this, but I haven't seen any ISP's take notice or do
    • Why would they realy care about how many 'puters are connected? My guess is if you have one machine running squid properly configured, it'l feed 10 internet users with less traffic on the ISP's network, than the scans to port 135 generate inbound. A lot of the adds for broadband advertise multiple comoputers on the internet at once as a sales feature. I've actualy chatted with the wife via yahoo messenger while we were both at home!
  • Ciscos's 675 modem/firewall comes with the DSL in this area. Cisco publishes security vulnerabilities frequently, but will only give updates if you have a Cisco contract, for more than $200. So, vulnerabilities go unpatched. Cisco says the telephone company is its customer, not the user. The telephone company has often been cited by the Oregon state government for bad service. The telephone company certainly will not support another company's products.

    • Cisco's products have a curious quality: They die! [] And you can't even read the death web page unless you pay Cisco money. This has been a VERY high total cost of ownership product. And now Cisco wants users to buy something else.

      Why buy a product from a company that kills its products? Why buy a closed-source product? Frankly, I think there will come a time when there are no closed-source products.

      I may not be able to defend myself now from aggressive business practices like those of Microsoft and C
  • Netopia R910 (Score:3, Interesting)

    by Detritus ( 11846 ) on Saturday September 06, 2003 @12:44AM (#6885656) Homepage
    One possibility is to spend some more money and get the low-end model in a series of routers manufactured by a real router company. After having problems with Netgear and SMC, I bought a Netopia R910. It runs the same software as their more expensive routers. The firewall features, while not as fancy as what you can do with a dedicated PC, are adequate for my needs.
  • Personally I'd never put one of these on the open Internet and expect to be secure.

    That said, I do have a Linksys packet filtering router that I use behind an OpenBSD packet filtering bridge.

    It makes more sense to have my servers sitting behind the bridge, and my desktops behind the router. I think Zwicky et. al in Building Internet Firewalls call this a "screened subnet."

    Having the packet filtering bridge operating on the outside edge of your network means that the number of people who have access to

  • by WoTG ( 610710 ) on Saturday September 06, 2003 @01:46AM (#6885870) Homepage Journal
    but the best trojans make OUTGOING connections to IRC or other systems. So, assuming that your NAT functions as advertised, your network is protected from all remote attacks. However, if an internal machine gets a virus or trojan through email or installing bugged software, you still have a serious security problem. NAT's by default, let internal machines make any connections to the outside that they want.

    So, turn on or add a firewall if you really are concerned. Not that that's a 100% solution either...
  • by Anonymous Coward

    Interesting, I just finished setting up this [] on one of these [].

    I was pretty damn impressed with m0n0wall, it's freebsd-based and fits on an 8MB CF card, and has a nice web interface. Of course it's free software so you can hack it and improve it all you like (you need another FreeBSD box to do it on).

    Check out this combo, it's the best of "play and play" and "high quality free software" in one Institutional Green sheet metal case!!

  • by pbannister ( 221251 ) <> on Saturday September 06, 2003 @04:03AM (#6886210) Homepage

    I too have wondered if there were any exploits for consumer NAT/firewall boxes. Judging from posts so far, it would seem that at least there are none known :).

    I started using the Linksys cable/routers when they first came out. I have insisted that all my neighbors, friends, and family with fast connections use a Linksys box (or similar).

    There are a few points to bear in mind:

    1. Most crack attempts are from brain-dead script kiddies.
    2. Hardware firewalls fail-safe, where software firewalls fail-unsafe.
    3. You don't want your average folk running only a software firewall.

    Observation (1) comes from running with both a Linux and Windows box exposed directly to the Internet. Both boxes had all unnecessary ports closed, were up-to-date on all patches, and carefully monitored. Neither machine was ever compromised. Periodic review of the logs showed a remarkable lack of intelligence on the part of the attacker. Practically all the activity was from a small number of popular crack-of-the-month scripts. Tracing the attacks back to their source - and getting the script kiddie kicked off their account - was seldom difficult.

    So practically speaking, we don't have to worry about ultra-sophisticated attacks. The vast majority of script kiddies lack the needed intelligence.

    Keep (2) in mind when you weigh the risk of failure. If a software firewall fails to run (for whatever reason) most likely your machine will be completely exposed. If the hardware NAT/firewall fails you will be safe (if without internet access). The software on your PC probably changes regularly. If any of those changes disables your firewall, the you might first notice when your machine is already subverted. The software in your NAT/firewall box never changes (discounting upgrades) so the chance of failure is less.

    Keep (3) in mind when evaluating effectiveness. Most folks with fast connections are not techies. A solution that works well and reliably for the bulk of the population is in the end far more effective.

    • "So practically speaking, we don't have to worry about ultra-sophisticated attacks. The vast majority of script kiddies lack the needed intelligence."

      I remember feeling like this. Safe and secure behind my impenetrable shield of carefully tweaked and tuned software and hardware firewalls/NAT routers which was continually monitored and kept up to date. Sure in the knowledge that the only incidents I would have to deal with would be caused by office staff installing the "latest aquarium screensaver" and e

      • "I basically live paranoid, but that doesn't mean I'm wrong. :)"

        How do you know the people who are out to get you aren't TRYING to make you paranoid?

        (Waits for brains to implode wrapping themselves around THAT one)

  • I just tried out this floppy distro called BBIagent [] and it's pretty easy to setup (GPL too!). You configure it through a java window and it's much cooler then my old linksys box. I hate to say it but one of the cool features is a live graph of my incoming/outgoing. There's also way more features.


    PS. I'm not affiliated with them in anyway, blah blah blah...
  • Not really (Score:4, Interesting)

    by Halvard ( 102061 ) on Saturday September 06, 2003 @08:02AM (#6886563)

    I know several people that have had problems using these. Not counting the problems with locking up by going for an URL on some (Linksys?), most people not bothering to change the default password and service providers or users or consultants turning on (or not turning off) the web management interface on the WAN side, these devices are designed to be used by people that have no business setting up and configuring firewalls.

    I've seen them directly compromised where someone broke in, changed the password AND disabled the public interface. Additionally, people and frequently small businesses stick servers behind them, whether just forwarding a port or using the DMZ option. Great, leave an patched or unpatched Windows box accessible on every port sitting there fat dumb and happy for attack. And leave it on your LAN where it can be used to stage an attack on everything else on your LAN and everyone else in the world.

    Of course I've also come across Cisco routers improperly configured to DMZ an Exchange server where every port except TCP 23 was forwarded and of course, it got owned.

    My point is that these devices provide a very false sense of being immune to attack and an "army of know-it-all experts" ranging from jr. high schoolers to 60 something retirees that really have little or no knowledge. Somebody sets up four of these things and they are an expert. It's like reading the first paragraph of "War and Peace" and declaring yourself an expert on Russian literature.

    Sometimes they are better than nothing, but they are worse than nothing when left in their default configuration or setup in a totally insecure way,leaving the "expert" confident that they are protected.

  • Maybe yes, maybe no. (Score:3, Informative)

    by FreeLinux ( 555387 ) on Saturday September 06, 2003 @10:55AM (#6887153)
    The consumer level firewalls that you mention can be secure but, they can also be compromised depending on the situation. The most important issue is the proper setup and on going maintenance of any security device. You cannot hope to be secure with a "fire and forget" security solution.

    The first issue is proper installation and configuration. Does the installer really know what they are doing and why? In many/most cases, the answer is no. The initial default configurations of these devices is usually very secure using a combination of NAT, which does indeed increase the level of security, and restrictive firewall rules. However, far too many people find the default configurations too restrictive for their needs and start opening holes in order to permit certain desired services like gaming. This is where the problems start. As unknowing installers open various ports or enable port forwarding or installing certain machines in "DMZ" zones the inadvertently open their systems up to the world.

    The second issue is with the actual OS of the device itself. There have been a few vulnerabilities in the devices that you mention that allow for compromise of the actual firewall. I have personally found two Linksys devices that were compromised and reconfigured as open proxies for the purpose of relaying spam. The vulnerabilities were known and there were fixes available to resolve the issue but, people frequently do not know about these vulnerabilities and the firmware updates are not applied. In most cases they are never even aware that they have been compromised. Do you know how to determine if you have been compromised and how often do you check to make sure? So, regular maintenance is very important but very few ever check for, let alone install firmware updates.

    The biggest issue is a true understanding of the risks and how to defend against them. I frequently see "qualified" network engineers with years of experience who still do not completely grasp the many facets of the IP protocol and how it can be used to invade a network. This does not however impact their belief that they are effectively installing and configuring firewalls of all varieties(shudder).

    To answer your question directly, depending on the precise situation and the requirements of the network, a Linksys or Netgear firewall can be just as secure as a CheckPoint firewall but, all three must be configured correctly, monitored constantly and maintained regularly.

    A thorough understanding of TCP/IP and its security is the most important step towards true security and this is in fact what most people lack. Look at this [] article asking about private IP addressing and the slew of comments that illustrate the person does not even understand subnetting. Yet, I'll wager that most of these people would not think twice about setting up a firewall and probably regard themselves as "experts" in network security.

    The actual firewall is not as critical as the understanding of the firewall. Switching from Linksys to a Linux firewall isn't helpful if you don't truly understand what you are looking at with ipchains -Lvn or iptables -Lvn. In fact, if you don't truly understand the many facets of securing an IP network as well as hardening the Linux OS, you are far better off with the Linksys. At least, in the default configuration, it is more likely to be secure.
  • Its the same thing! (Score:3, Interesting)

    by josepha48 ( 13953 ) on Saturday September 06, 2003 @02:03PM (#6888209) Journal
    Supposedly Linksys, uses Linux in their devices. There was a discussion about this on the linux kernel mailing list or slashdot a little while ago.

    Anyway the principal is the same in both cases. Both Linux and these devices offer you a firewall and both offer you NAT and a few other features. The NAT devices offer you ease of configuration and ease of use, while Linux, BSD, or any other UNIX type OS that has built in firewalling offers you a little more control over the firewalling. AFAIK you cant deal with frag packets in these NAT devices and specify various tcp flags or things. All they do is allow or deny various types of traffic. Also you cant set them up to do DNS / mail like you could a Linux / BSD system.

    In the end it is a matter of preference IMHO and affordability. If you can afford one and don't want to deal with all the updates that you'd be applying to a Linux box or BSD system then that would be the way to go.

    • assuming this link is still active read here about netgear and smc &ncid=74&e=4&u=/cmp/20030906/tc_cmp/147000 57

      In either case you have to keep them updated

  • Words of Warning (Score:3, Insightful)

    by schulzdogg ( 165637 ) on Saturday September 06, 2003 @04:26PM (#6889074) Homepage Journal
    I have a linksys router thingy, and It sits in front of several computers and other networked home appliances (Tivo, Playstation).

    It works great, never had a problem with it at all, but...

    I have a linux server running on that network and traffic on port 22 is forwarded to the linux box. Add an old version of sshd and viola! Rooted.

    Because I was behind that firewall though I didn't pay as much attention to the box as I should have and it took me a week to realize something was wrong.

    Moral: The firewall can't protect you from yourself. You still have to be carefull behind it.

  • They're good, but... (Score:3, Informative)

    by vasqzr ( 619165 ) <vasqzr@n[ ] ['ets' in gap]> on Sunday September 07, 2003 @01:09AM (#6891411)

    A good firewall would mean setting up a Linux/BSD box, putting a couple NICs in it and setting it all up, right.

    But 95% of the people who read a couple FAQs or books won't do it perfectly.

    So the small appliances work great, as long as you can live with their limited functionality. If you just want 30 users to surf the web it'll be fine, but getting servers etc involved can be tricky with some models.

    The worst thing is when they have poor security by default. We used to scan entire IP blocks, looking for open telnet ports, and we'd just use the default logins to get in. Anyone remember 'wradmin'?

    You could telnet in, shut the DHCP off, or disable routing, telnet to other computers/printers inside their private networks, if it was an ISDN router you could change the dial out phone numbers...

  • by lostchicken ( 226656 ) on Sunday September 07, 2003 @06:40PM (#6895654)
    I see posts telling me that I should understand my network and my device and that there are holes in security, but my question is if you've got one of these routers with remote management off, no ports forwarded, block WAN request, etc, what can anyone do?

    I hear people saying, well they run Linux, and Linux is hackable. With no ports open, how is it hackable? (DoS attacks don't count and neither do trojans running inside)
  • How about an OpenBSD firewall? Secure by default, easy to patch, and you can actually do it all by reading the man pages and the OpenBSDFAQ. I consider myself an internediate Linux user but I was never able to get a Linux firewall up and running but OpenBSD 3.2 was simple and well laid out. The man pages spoil you w/ their easy to understand language and completeness. I've bought a few Open Source OSs' but OpenBSD was the best investment by far. Uptime is at 114 days, using about 34 megs of RAM and t
    • BSD firewalls are very nice. Haven't popped OpenBSD on a box, yet, but I ran a firewall with FreeBSd before and it worked beautifully. While everyone else on our Adelphia network (about 2 years ago) was getting scanned and attacked, we were sitting pretty. Worked right up until the machine got fried in a lightning strike.

      Of course, I'm now looking into my next setup, which'll like have my OpenBSD box (installing in the next couple weeks) and then a firewall, followed by another firewall, and then my other

  • by wraith0x29a ( 565168 ) on Monday September 08, 2003 @10:46AM (#6899701)
    I used to build Linux based NAT/Firewall machines for small businesses. One of my clients complained that their network had been (badly) compromised over the course of a week and blamed my product for this. The language he used was unacceptable even by my broad standards. After a hurried flight to his office (in another country) I noticed that nearly every PC on his network had a shiny new modem plugged into the wall. A quick check and - yes - no firewalling on any of these NT4 machines. It turned out he had been having complaints that the offices' 56kbps modem connection serviced by our NAT/Firewall box was too slow for the forty or so machines on his network to use concurrently so in an effort to save some money he had paid his daughter's boyfriend to install modems in all the office machines (rather than upgrade to DSL as I had suggested at installation time). This ham-fisted luser had set the modems up for dial-on demand then misconfigured some services that kept the lines up 24/7 allowing some script-kiddie to wreak havok on his network. My client's argument was that as our NAT/Firewall box was a security product it should have protected his network whatever other changes he made to the network and that we were liable for damages. Rather than risk talking at this juncture I simply pointed out a section in our four-page, large print, plain-english manual that was sitting, unread, on his desk - 'Under no circumstances allow computers or devices on your network a direct connection to the Internet. Using other methods of Internet access such as a modem will completely bypass the security features of our product.' I aslo helpfully drew his attention to the bit in our support contract that said 'On-site support visits related to issues arising from an inability on the part of the purchaser to read the included documentation will be billed at our consultancy rates of 150 per hour (or part thereof) including travelling time and expenses. These costs are not covered by the purchaser's support contract.' He'd started going purple by this point so I thought I'd do him a favour and warned him his next phone bill may be a wee bit high. "Oh, no problem there" he said, relaxing a little, "Dave used a free Internet Service Provider". "Ah", said I, "is that free access or free calls?" "Er" he said then called British Telecom Billing. "What's our next bill currently standing at?" he enquired politely. The next sentence was complex and largely unintelligable save from the phrases "bastard bloody bastard idiot bastard boyfriend", "so far up", "chew my toes", "bloody girl too" and the concluding "Gnnnaarrgh!" In a rare moment of BOFH compassion I made him a cup of tea at this point, coincidentally taking me across another 150-an-hour-or-part-thereof boundary. The moral of this slightly rambling story is.. 'a network is only as secure as it's dumbest user whatever NAT/Firewall you install'.
  • The NAT boxes will stop your garden-variety worm searching for vulnerable services on a default-configured Windows box, provided you don't open those ports.

    But a lot of them support "UPNP", which allows programs on the to automatically open up ports they need. This is a great convenience, but you're now giving the keys to your network to any random Windows program. Now any trojans don't need to actively call out -- they can just open up your firewall FOR you and wait for connections. This strikes me as
  • OK, I have a separate firewall, two NICs, running iptables.

    The question I have is this: I have some ports open from the outside, for specific purposes (ssh, for example). Now if I'm going to have ports open, what do I need to have blocked to avoid spoofing?

    For instance, I currently am blocking incoming traffic:

    1) with a source IP of 127.x.x.x
    2) with a source IP from inside my firewall
    3) with any other non-routable source IP

    What else do I need to block, before forwarding it on to the appropriate machine/
  • I've got a switched hub at home which has recently started exhibiting very bizarre behaviour, sending huge streams of packets even though the connected machines shouldn't be sending data.

    Shouldn't meaning that any machine I plug (3 different OS's) into the switch and it starts a blazing trail of packets. Plug it into itself (normal port into uplink port) and it blazes away too. A reboot fixes it.

    I haven't figured out the cause yet, or why... but it often seems to start with a lot of data passing through

Logic is the chastity belt of the mind!