How Do You Handle New MS Word Vulnerabilities?

chipperdog asks: "With yet another zero-day exploit of MS-Word document files, what are fellow system admins doing to protect themselves against these threats? I have been blocking all .doc and .dot at the mail and proxy servers until malware scanners have signatures to detect and block the malicious files. Of course, this caused a uproar with the users, as there were continuous calls like: 'When can I send and receive Word files again' and 'I can't get anything done if I can't send/receive Word files'. Any suggestion of sending documents in different formats (like rtf, html, txt, or pdf) results in even more creative user 'feedback'. Has anyone done anything creative in their handling of word files — like having qmail-scanner pipe all .doc attachments through something such as wv to convert them to a less exploitable format?"

You can't...

You can't suddenly cut off the exchange of Word documents in any modern business. Unless you can justify bringing your company to a halt over some vulnerabilities with no real-world risk, you just can't do it.

At least for now we filter...

All attached DOC files are filtered and placed in to a users quarnetine folder (which they have access via a web browser). Simple permissions keep them from accessing the file itself until it can be checked. Once checked, permissions are changed and the user can pull the document.

It's frustrating for the end user as they don't have instant access to their attachment (sometimes there's a 4-hour delay before the file can be manually inspected -- still waiting for some def-files!) and it's taxing my staff time-wise to do this (we've got better things to do than check for any monkey-business in word documents). We've suggested everyone convert to PDFs and send THOSE and it's been working but it's still a disruption.

strings

% strings $1 | less

(I'm almost serious).

Rename the files

Tell the users to rename the files to .dat. That's what we do for sending files around that our mail server blocks. The content of the e-mail would tell the user to rename the file back to .doc. We often send vbs scripts around that we rename to .txt to get around our mail server.

Re:Rename the files

I don't presume to know your job, but if your users need to subvert the protection scheme in order to use the system for its intended purpose and do their jobs, the protection scheme needs some serious work.

Open Office

It's amazing how, we've been fighting this uphill battle to get our users to use Open Office, and now all of the sudden, managers are calling us to make sure all of their users have it. :-) Some days, I like my job. :-)

The stick.

Coworker of mine has a sawed off hoe handle, which he maintains was useful for maintenance on an obscure now-obsolete color proofer. Routine application of this to users is beneficial in stopping the spread of these documents.

Heh.

The bulk of our traffic here is excel and powerpoint, so limiting word documents hasn't been a real problem. Additionally, corporate used to require stupidly high end router hardware in all parts of the building which was abusive on the budget, but, at times like this, comes in handy.

Wow... glad you don't work for me.

Killing your company's productivity by not allowing the exchange of information? A big no-no. Plus it is all-to-easy to get around (rename the extention, zip the file, etc).

A better solution is to educate the users - send out a mass email explaining the vulnurability, that you shouldn't be opening and doc's you aren't expecting. If you do it is your own damn fault and the timeliness of the fixing of your machine can not be guaranteed. There is no reason to choke business as you have and quite frankly the users have every reason to be upset.

Re:Wow... glad you don't work for me.

So what to tell the people in HR that are expecting resumes?

"Zero-day"

Does "zero-day" still mean what it once meant? People are calling exploits "zero-day" weeks after they are available.

"Zero-day" means it was released today. Every exploit was "zero-day" sometime, but ceased to be the next day.

Zip the files

Any suggestion of sending documents in different formats (like rtf, html, txt, or pdf) results in even more creative user 'feedback'.

Then tell them to zip the files and then they'll get through the filter. Problem solved.

Its pays to be thorough

We nuked the site from orbit. It was the only way to be sure.

The simplest way.

OpenOffice.org.

Quarantine

When we have viruses exploiting Word files, part of our security team sends out a notice that says we're temporarily quarantining the files until we can have them cleared. But really, you can't indefinitely stop word files from coming in.

I'll admit I'm too lazy to read the exact detail of the exploit, but shouldn't this whole situation be alleviated by good, layered network security anyway?

Why not...

...turn off word macros for the majority of your users who do not need them. For those who do give them an hour long or so seminar on the safe way to work with word macros, including opening (or not) files from unknown/untrusted sources. I'm astounded at the level of ignorance many people claiming to be knowledgable UNIX/Linux admins have with regards to running what they consider to be a little kiddie playground of a server OS yet they seem to have all sorts of trouble. If the OS is for idiots as you claim then you should have no trouble using group policies to enforce these rules. If you cannot enforce these group policies then perhaps it is you who is the idiot and not the OS.

Honestly

I'm a windows network admin, and I made a group policy to deny people downloading new word format files, atleast until they put a good patch out.

Scan, rinse, repeat.

We keep the AV scanner at the gateway up. We keep the spam filter at the gateway up. We keep the AV on the desktop up-to-date.

Right now there's no good RPC-exploitable worm for Windows. Any word-based infection is going to be localized to a single machine (or, at most, to those machines a user has remote local administrative rights on). So, we watch. We stay at yellow allert, and we don't panic. Because right now, there's nothing to panic about. The ability to spread a virus/worm/mal* to a single machine isn't exactly a huge danger. We already have that every time someone sends us an URL.

Panic on your own time.

stripping macros

Wouldn't it be possible to automatically strip all macros from the documents? Of course, some documents wouldn't survive the alteration unscathed, but for most of the documents I don't think the end users would even notice a difference.

Sir, You Are A....

Blocking all doc files? Too funny. What a jerky self-important moron of an admin. Learn how to weigh risk and reward, dude. You clearly have no clue. Sounds like you have a hard-on for Microsoft and are trying to make a point.

Good luck with that and your next job, which is right around the corner. Maybe you can refuse to flip any burgers that have trans fat in them.

I'm just shaking my head and rolling my eyes. BOFH indeed.

docs.google.com

upoad to docs.google.com then download from docs.google.com

MIMEDefang.. customize mimedefang-filter

Setup MIMEDefang to convert M$ word attachments to PDF using openoffice.
Any attachments with a .doc extension or a mimetype of application/msword go through this process.
Also to reduce the overhead, get the sha1sum for the word document, and save the pdf to .pdf
Before any documents are converted with openoffice, get the sha1sum. if a .pdf already exists, use that file.

This stills allows people to get the content, which is most of the time, all they want.

There is also a program called antiword that will convert ms word documents to text, PDF, or PostScript.
But openoffice does a better job.

Re: Antiword or Catdoc

Well I use Linux so I dont have MS Office but I extract the text from MS Word documents using Antiword or Catdoc and then read them in Vim.

Antiword: http://www.winfield.demon.nl/ [demon.nl]
Catdoc: http://www.45.free.net/~vitus/software/catdoc/ [free.net]

Add this to your .vimrc to make it automagic:

autocmd BufReadPre *.doc set filetype="msword"
autocmd BufReadPost *.doc silent %!antiword "%"
autocmd Filetype msword call s:MyMSWordSettings()

function! s:MyMSWordSettings()
        set readonly
        set hlsearch!
endfunction

For RTF documents, check out UnRTF: http://www.gnu.org/software/unrtf/unrtf.html [gnu.org]

Nothing.

I only use Word at work, so it's not my problem. You can't just stop using Word without possibly losing money, so it's worth the risk. It's not like I'm going to open any emails from people I don't know anyway.

The answer is obvious.

With yet another zero-day exploit of MS-Word document files, what are fellow system admins doing to protect themselves against these threats?

Yet more evidence of the truth and beauty of the Church of Emacs [dina.kvl.dk].

Or, if one is into truly antediluvian forms of worship, Ed, man! !man ed [gnu.org].

For all Office users, there is a patch here!

It's quite big but it'll solve your MS Office security problems.

http://download.openoffice.org/2.1.0/index.html [openoffice.org]
 

I must be missing something awfully obvious...

What about using the Word Viewer [microsoft.com]?

Simple

Simple. My employees know not to open any file that they don't know what it is. I really don't know how you can get any simpler or more effective than that.

Easily

It's a simple process:

• Buy a fat cigar and smoke it
• Hire a hooker
• Snort cocaine off her ass
• Play a game of blackjack with her
• Take some horse tranquilizers
• Sit in the corner crying at how futile life is
• Try to ignore the insects crawling under my skin

Sandbox as much as they'll let you

'When can I send and receive Word files again' and 'I can't get anything done if I can't send/receive Word files'.

If your users need to send/receive executable code from/to strangers (which is essentially what they're asking for) then you're in a nasty situation.

If you're the boss, one obvious thing to do is to make them sign something to the effect that the cost of cleaning up after their willful unsafe practices, will come out of their own paychecks.

Let's assume you're not the boss.

You can't trust scanners anyway; it's not a matter of today's particular 0-day-exploit, because there will always be exploits. You must assume that hostile code will be running (probably with full admin privileges) on those users' machines. Sandbox as much as they'll allow you to. Run MS Word itself inside a dedicated virtual machine if you can. If you can't, then run the Windows session itself inside one. Put those boxes on their own network, etc. The key is to accept the destruction, but also try to limit it to the people who are asking for it. It's ok if your company loses a few thousand dollars of work every week or so from a few bad users -- you need to keep from losing millions, and hopefully in such a way that when the boss comes screaming about the thousands, you have something positive to point to.

And, if you can, keep memos about complaints (or prohibitions from above) as a record to show that you were not allowed to really fix the problem: you don't just want credit for preventing the big disaster; you want absolution from blame for the little disaster.

You should be limiting .DOC email exchange anyway

Even ignoring viruses/worms altogether, it's not a good idea for users to be exchanging .DOC, .XLS, and .PPT files through email. People do this for two reasons:

1. Exchanging finished documents for reading. PDF is better:
   1. It can reproduce the results exactly.
   2. It doesn't include Word's "change tracking" information which can cause embarrassing leaks.
   3. It's a standard with many interoperable implementations.
2. Exchanging in-progress documents for revision. At least for stuff limited to your company, a version control server (like Subversion [tigris.org] with friendly TortoiseSVN [tigris.org] clients) is better:
   1. Doesn't cause email storage to grow enormously. Instead, a server actually meant for this kind of thing stores only deltas. And only one copy of each document - on most mailservers, the disk space consumed by an attachment is proportional to the number of recipients.
   2. Lets you easily find the latest version of a document. ("Did he send me another copy after this? I'm not sure.")
   3. Lets you easily retrieve any previous version, see changes/authors/checkin comments. (I don't trust Word's built-in change tracking, and you shouldn't either. Its security model is flawed, and I don't think it's reliable to begin with.)
   4. Supports locking/unlocking documents to prevent conflicting changes.
   5. With some setup, supports diffing and merging [tigris.org] office documents. You can maintain branches!
   6. Supports searching - where I work, we've plugged in swish-e [swish-e.org] for full-text searching over our documentation repository.

I wish my company would just block all .DOC and .XLS files sent from one employee to another. It'd force them to use the documentation repository and save us all a tremendous amount of pain trying to dig through email for the right version of some Product Requirements Document. It'd also stop the whining from people complaining about hitting their email storage limits all the time.

Obscure Onion reference?

I only run MS Word in my hermetically sealed house, which I never leave.

I've got an idea

Let your users send and receive .doc's and therefore get their jobs done. Explain to them (maybe through a corporate memo?) the risks with .doc files and not to open any .doc files that they don't know for certain are from reliable sources. Eh?

I for one make my company's employees and their ability to get their jobs done quickly and effectively my first priority. Forget about the exploits. Don't let M$'s insecure software make your workers less effective!!

IMO blocking .doc's altogether while you wait for your malware filter to be able to catch the exploit is obviously overkill.

Remove the root cause

We do not use Microsoft Word at my place of business. This is therefore no longer a concern. If any sysadmin thinks this is a problem, it's clearly time to approach the PHB with it in terms that they will understand. Something along the lines of, "Yes, I'd love to tackle that super-urgent issue of yours, but I'm too busy fighting these n MS Word vulnerabilities" where n is greater than zero. That ought to do it.

Risk management

Remember, everyone in your company has a job to do; your job is to help them do their jobs. Sometimes employees will be impacted by security issues; but when their time is spent primarily working around your paranoid security restrictions, then you're hurting your business. Right now, you're more likely to either 1: Get fired, 2: insult an important business client, 3: piss off a valuable employee who will decide to move to a company who doesn't have an @$$h0l3 running their network...

It's good that you can disable word documents from email in the event of an outbreak; if, and only if an outbreak does occur, then disabling word documents from email might be your only option.

The other thing to consider is that, if a virus starts spreading though word documents in email attachments, you're going to start seeing a lot of SPAM with word documents attached. Consider being more restrictive to SPAM with regard to attachments.

Open Office on a Mac

Either be very diligent with your backups (which you should be anyway) or just don't use it. "Viruses" and general issues with computers (MS products specifically) are the counter part to 'other people on the road' when driving your car. You either put up with the dangers and prepair yourself for the pain or simply don't get involved.

Fortunately with computers you can just make backups and only loose a day or two of production if everything goes to shit. Not so possible with a head on collision at 50mph.

Easy solutions are sometimes the best solutions

How do I handle it? Use OpenOffice.

Who needs Word?

I still use WordPerfect for my WP ...

What Word Documents?

I stopped using Word back in 1997 when I couldn't get a simple (C) to not be turned into a copyright symbol in a document. After several hours of searching help and disabling what seemed like hundreds of preferences that began with "auto," I pasted the document text into Netscape Gold's HTML editor and never looked back.

I've given the PHBs plenty of trouble since then by not accepting DOC files (or later on Excel files either). They can't figure out how to save in any other format (which was my suggestion the first few years).

To make a long story short, they've finally taken to just printing the document for me and e-mailing it to everyone else.

I sincerely hope that this rash of zero-day viruses will finally get them to consider ODF, but it'll probably take another 3-5 years before that epiphany hits any of them.

Risk

Apply the the standard, Threat/Likelihood/Impact risk model before you start on these things.

So you block Ms-Word, what's the threat (and it exploited yet which is Likelihood) and finally what's the impact of the threat. Now apply this your actions. ...

Another thing I'd say various IE issues are more of a risk than little exploited (to date) in Word.

Given the time you are spending, the impact you're having on the business, is your 'fix' worth it?

Filtering...

The trouble with trying to filter, is that the word format is a binary blob without any documentation...
It's quite easy to filter out things like the jpeg exploit, just try opening it with a jpeg library on the filter server, the exploit jpegs won't load properly and error, or you can convert them on the fly to another image format.
Ofcourse this brings up a risk to your server, but the risk is much smaller, the server is likely to be hardened, could be running many different os's on several different hardware platforms, won't be running the code as a privileged user, and could easily be running it inside of a chroot. If you were to use something like grsecurity on linux, you could make sure the risky parsing code ran inside of a chroot, did not have the ability to write anywhere (except its input/output pipes) and did not have the ability to open sockets or execute any additional programs.
When you know the format, you can cut out a large percentage of exploits by validating the contents of the format against what the specs say it should contain, you can then sanitise parts of the file if necessary, or convert it into another (compatible) format.
Ofcourse it's not foolproof, but it raises the bar much higher.
This is a very good reason not to allow unknown binary data to be transferred in/out of your network.

What I do...

Well, I typically Wazoo worry about it. I mean, hey, Wazoo someone wants to cause harm to my Wazoo documents, then clearly that's Wazoo issue, not mine.

I mean, hey, Wazoo security isn't my job ... Wazoo?

Signed, N

Re:Simple:

Yeah, OK. Now, does anyone have a reasonable solution?

Re:I don't

Yeah, get a Mac to run Word on. :P

Re:I don't

At least one of the three recent Word exploits affects Word for Mac as well.

Also, to the original question:

Scanning .doc and .dot files does little to no good for the most recent vulnerability. Windows is coded to open correctly formatted documents with unknown extensions with Word. So all I'd have to do to get around your filter is rename the document to: Exploit!.iamnotavir.us0 and if someone is silly enough to double-click it, they'll be subject to whatever maliciousness I can inflict on them.

From the e-week article:
"Do not rely on file-name extension filtering. In most cases, Windows will call Word to open a document even if the document has an unknown file extension. For example, if document.qwer contains the correct file header information, Windows will open document.qwer with Word. Filtering for common extensions such as .doc, and .dot will not detect all Word documents."

Re:I don't

Being an ex-network administrator, I have come to the conclusion that it is us who save the company tons of money by keeping it safe from exploits. By practicing good security measures, anti-virus installations, ad-ware remover, etc, it usually cuts down considerably on the amount of work it takes to keep the network infrastructure free of viruses and spyware, allowing time to focus on other important factors, such as Word exploits, migration from windows to a linux OS if all it requires is word processing, etc.

Here's hoping Vista lives up to the hype that under good security measures, it will be somewhat secure. Otherwise, there are alternatives such as migration to linux and OpenOffice and such, which does not suffer from as many exploits that Windows and Office does.