Malware Evades Detection By Counting Word Documents (threatpost.com) 70
"Researchers have found a new strain of document-based macro malware that evades discovery by lying dormant when it detects a security researcher's test environment," reports Threatpost, The Kaspersky Lab security news service. Slashdot reader writes:
Once a computer is compromised, the malware will count the number of Word documents stored on the local drive; if it's more than two, the malware executes. Otherwise, it figures it's landed in a virtual environment or is executing in a sandbox and stays dormant.
A typical test environment consists of a fresh Windows computer image loaded into a VM. The OS image usually lacks documents and other telltale signs of real world use [according to SentinelOne researcher Caleb Fenton]. If no Microsoft Word documents are found, the VBA macro's code execution terminates, shielding the malware from automated analysis and detection. Alternately, if more than two Word documents are found on the targeted system, the macro will download and install the malware payload.
A typical test environment consists of a fresh Windows computer image loaded into a VM. The OS image usually lacks documents and other telltale signs of real world use [according to SentinelOne researcher Caleb Fenton]. If no Microsoft Word documents are found, the VBA macro's code execution terminates, shielding the malware from automated analysis and detection. Alternately, if more than two Word documents are found on the targeted system, the macro will download and install the malware payload.
Easy solution to avoid this malware... (Score:4, Insightful)
Don't use Word.
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Disable macros. Allowing macros to do things that are harmful is a massive design flaw.
Re: Easy solution to avoid this malware... (Score:5, Insightful)
Even if you use LibreOffice I am sure you have word and excel documents lying around. If you do real work or a college student you are going to be emailed office documents.
Re: Easy solution to avoid this malware... (Score:5, Insightful)
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Have you taken a college course
not since the advent of PC, but I know even some grade schools seems to require Microsoft junk and tests via WEB Pages. That only indicates to me the quality of our (US) education system, seems 'real' teaching went out of style in the 80s.
had to deal in a "business-to-business" interaction at all in the past 15 years?
Everyday, what I want to say is either in the email body or in a text file or rarely a Libreoffice doc. If I have to deal with Microsoft formatted files they can deal with file formats I prefer.
Re: Easy solution to avoid this malware... (Score:5, Insightful)
Your point still stands that there are plenty of ways to deal with these files without having Office installed. That's the key here, it's not that the files are particularly dangerous, it's the interpreter that runs the macros you have to worry about! Plenty of solutions to deal with these formats available without having Office installed, Office 365 as you mentioned, Libre Office, Google Docs. MS software is like heroin, it feels pretty good when it's doing what its supposed to, but when everything goes wrong you're going to get hurt bad.
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I have more LibreOffice and PDF files "lying around" these days than Word and Excel,
So what you're saying is you have Word and Excel documents lying around even though you don't use Microsoft? You wrote a lot in your counter argument only to agree with the GP.
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[~]$ find -iname '*.doc' -o -iname '*.docx'|wc -l
72
I don't even have any form of office (libre, open or ms) installed.
Re: Easy solution to avoid this malware... (Score:5, Funny)
If you do real work or a college student you are going to be emailed office documents.
I'm not sure I see the connection between doing a college student and being emailed office documents.
Re: Easy solution to avoid this malware... (Score:1)
How else are you going to get served your paternity test sub peona?
I have a out of this world solution (Score:4, Funny)
Researchers should store 3 word documents on their systems.
Re:I have a out of this world solution (Score:5, Insightful)
Brilliant. Pure genius. Nobody ever could come up with this idea.
No, but seriously. The point is that this thwarts automatic detection tools. Of course, if a human is examining the malware, he will dissect it and analyze it and quickly realize that it counts documents. The automated tool will only notice that it does ... well, nothing.
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Thanks I'm brilliant, I knew not having a high skool diploma would be useful one day.. Speaking of which any one running these systems should be able to create a script/program to continuously create/delete word documents and randomize the count of documents in the system at any time.
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This is probably what is going to happen now. Until now, there wasn't really much of a reason to do it.
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They probably dumped a file of each type into the sample set, to see what kind of documents the malware encrypts and in what way. Hence it is looking for TWO Word files. :)
Re:I have a out of this world solution (Score:5, Insightful)
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This is rather odd, considering how manual malware reverse engineering works. Usually when you get a sample to dissect, you already know that it's a bogey. So it not doing what it's supposed to do is a quick way to become even more interesting, and finding that reason shouldn't take a good AV researcher more than an hour, tops.
It also doesn't really add to the complexity of the analysis, creating/copying a handful of documents into your VM isn't that big a deal, what you'll probably do is to clean up, copy
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Think about it, if you've got a backlog of hundreds or even thousands of quest
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I can tell you exactly how much time a reverse engineer invests in a file that may or may not be malware: Zero seconds. There isn't even close to enough time to start looking at even a tiny fraction of all the potentially dodgy files that make it past the attention of an AV team. And there isn't also any need for this, we do have very sophisticated automated tools that do pretty much what you describe, create a VM environment and run the file. Well, it does a bit more than just run it, but let's keep it at
Re:I have a out of this world solution (Score:5, Interesting)
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Oh well, guess they probably will now!
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Researchers should store 3 word documents on their systems.
Seriously, using an empty install of Windows, in a VM, as a "Honey Pot" to catch malware is really lazy! Put something in there that would fool a casual human. ;-)
Then maybe you can fool the -next- version of malware.
Stupid comments aside... (Score:2)
This is really smart. Sure, you can not have Word and or have more docs but the detection of a real environment will just change. Kudos to the dev for thinking about this, even if it is virii.
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You could image a real-world computer and use that to make test environment templates (obviously remove any documents that contain any real sensitive info).
Re: Stupid comments aside... (Score:2)
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Viruses. In English, at least. In Latin, it would be vira. Third declination, not second.
And while I can at least understand that people who don't understand Latin but somehow learned that -us becomes -i in plural (yes, if it's 2nd and masculine instead of neuter), where the fuck does that second "i" come from?
Re:Stupid comments aside... (Score:4, Interesting)
Viruses. In English, at least. In Latin, it would be vira. Third declination, not second.
And while I can at least understand that people who don't understand Latin but somehow learned that -us becomes -i in plural (yes, if it's 2nd and masculine instead of neuter), where the fuck does that second "i" come from?
Your answer is confusing, even though the result is correct.
Morphologically speaking, "vira" would be the proper plural precisely because "virus" is a second (not third) declension neuter noun.
Yet, it "virus" like "water" is uncountable so this plural is unattested.
But why do we always end up in this same Latin grammar and philology lesson?
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But why do we always end up in this same Latin grammar and philology lesson?
...OCD?
I have some too.
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Your answer is confusing, even though the result is correct.
It's actually not correct but that's because I'm not new here. The spelling was intentional.
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The stock images should be more comprehensive?
I can't imagine any malware could detect a stock image taken from a year of use.
Yep. Even if it was taken from a few weeks of use in a student lab the amount of effort needed for a virus to determine the false positives from the false negatives would become astronomical. It would either still infect some honeypots or greatly reduce the number of systems it could infect.
Basically the honeypots made it too easy as a real computer in use shows many signs of use like facebook access, random google searches, random cruft on the hard drives, etc.. This is a simplistic version. I could s
Ingenious programmers! (Score:3)
They make code do stuff before it's even executed these days!
But they could also have it look for cat videos. If even one is detected, it should definitely run no matter how many Word documents are found.
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Other AV just tests to see any changes in an OS and reports back findings to the AV developers.
What can a Word file do in such environments?
The evaded detection part can be as simple as not working when detecting a list of the most popular AV applications or software firewalls on an OS.
Next gen (Score:5, Funny)
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Large size increases likelihood of detection. The code to count .doc files is tiny. Facial recognition, not so much.
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Well, that pretty much sucks (Score:2)
Sux2bme I guess.
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I seem to recall that some versions of Word don't recognize files from other versions of Word as being "Word format".
When I've had to deal with places that only take "Word format" I've sent them several different versions due to the above (and with a PDF version, too). I've occasionally been thanked for my thoughtfulness.
Of course, keeping around copies of one file in several variations of "Word format" takes up a disproportionate amount of space, so I only generate them as needed.
Counting documents is doing something (Score:2, Insightful)
Am I retarded? It doesn't matter.
Counting documents is "doing something" If the automated system doesn't see the macro accessing the filesystem and doing searches on the filesystem, then the automated system is more retarded than me.
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'Retarded' may be a bit harsh - perhaps 'slow' might be more appropriate.
You're assuming that performing innocuous read only file operations is sufficient cause to flag the macro as being a virus.
Consider, for example, a legitimate macro which would present the user with a list of monthly sales reports. I haven't done spreadsheets since running Lotus 1-2-3 on a VAX mini computer, but your macro would essentially end up searching for 'SALES*.DOC' files - almost exactly what this one is doing.
Would you bar
we don't need no steenking word (Score:1)
Volkswagen virus (Score:2)
Thank goodness (Score:2)
I'm safe.
I mean, I use Linux and Mac so I'd be safe anyway, but if they made this virus for a real computer instead of Windows then I'd still be safe because my hard drives have zero Word documents on them.