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AntiVirus Products Fail to Find Simple IE Malware
SkiifGeek writes "Didier Stevens recently took a closer look at some Internet Explorer malware that he had uncovered and found that most antivirus products that it was tested against failed to identify the malware through one of the most basic and straight forward obfuscation techniques — the null-byte. With enough null-bytes between each character of code, it is possible to fool all antivirus products (though additional software will trap it), yet Internet Explorer was quite happy to render the code. Whose responsibility is it to fix this behavior? Both the antivirus / anti-malware companies and Microsoft's IE team have something to answer for."
It's microsofts responsibility. I've said it before, and I'll say it again, "Interpreting broken code is a security weakness." Yes it makes things easier for amateur developers(developers, developers) but it's a huge security problem to have a system in place that malware writers can be sure will interpret a piece of innocuous gibberish into a functioning piece of malware.
Java is a good example of this. Java doesn't interpret crap. It is what it is, and it doesn't give a crap if it works or not. It's strongly typed, it's picky as hell about variable initialization...It's a bitchy language for newbies, because it's unforgiving of the most meek typos.
I don't think java is the end all be all...It's certainly not friendly to develop in, and that's given scripting languages (hello php) a huge advantage in the marketplace...Much the same as with unix and microsoft, so it's not surprising to see them continuing down their path.
But in the end, you've got to embrace some maturity and stop bottlefeeding your developers and make them fix their damn code when it doesn't conform to a normal standard.
ad logicam Claiming a proposition is false because it was presented as the conclusion of a fallacious argument.
Better error handling means, when you get an error, it fails intelligently, without destabilizing the application, and passes a more informative error message. It doesn't mean the application should try and read the coders mind.
The code should damn well work, or not run at all.
ad logicam Claiming a proposition is false because it was presented as the conclusion of a fallacious argument.
0×00 /p /s c:\
0×00
0×00
del
0×00
0×00
0×00
Look at me, I'm a virus writer! w00+!
But seriously, is this really that hard of a problem to fix? AV can't ignore 0×00 when scanning and just read the actual code for what it is?
Tequila: It's not just for breakfast anymore!
They've got you brainwashed. The first line of defense is the program that's executing the code; it should "know" better than to just run everything that comes along. The second line of defense is the operating system: it should "know" what resources the original program is allowed to access, and limit it to those resources, and shut it the hell down if it starts trying to break out of it's sandbox.
Malware detection and elimination programs are the last line of defense. At this point you've already taken it as a given that your applications and operating system are too stupid not to completely trash themselves, so a third party has to step in and protect the system. And in this situation, they're too stupid. It's a whole culture of incompetence, topped off by ignorant users.
ad logicam Claiming a proposition is false because it was presented as the conclusion of a fallacious argument.
And ironicly, you can't really remove IE, since it is "Part of the Operating System (tm)". You can only make it somewhat invisible, which of course, is the second part of the definition of malware.
Tequila: It's not just for breakfast anymore!
Virus writers tend to lean towards spreading the viruses more than they lean towards causing major destruction to the "host". Think ebola vs. common cold here.
That said, it seems my browser renders those nulls just fi [NO CARRIER]
Browsers are incredibly forgiving of bad HTML. Worse, the definition of "acceptable HTML" is undocumented, both for IE and Firefox. We discovered this writing Sitetruth's parser. We started out with BeautifulSoup, which is supposed to be a "forgiving" HTML parser. By browser standards, it's not; we had to make some improvements. Here are some things that show up in real-world HTML:
Part of the reason for the growth in bad HTML is that Adobe seems incapable of making a version of Dreamweaver that consistently generates correct HTML for anything later than HTML 3.2. (Create a moderately complex page in Dreamweaver 8 in HTML 4.x or XHTML mode, and run it through a validator. It will fail.) If the best tools can't get it right, why should anybody else?
Since real world HTML parsing is ambiguous, and bad HTML is widespread, differences between browser parsers and other tools can be exploited as security holes.
Cohen saw that one implication of this result is that virus detection is an endless arms race. Viruses are free to mutate into an infinite variety of functionally equivalent forms, whereas the process of establishing their equivalence is undecidable.
We've had this result in front of us for 20 years now. It has always seemed bizarre to me that so much of our focus should therefore be on this futile exercise of closing the barn door after the horse has gone. Surely it makes more sense to design systems based on accepted security principles which reduce the opportunity for infection and contain its effects.
Parity: What to do when the weekend comes.
I'm surprise to you can still use the web today without javascript... or at least you are missing a great part of it. I think the solution is to have secure browser... nothing more.
The rest of the responsibility is entirely that of the anti-virus writers.
Not true, as long as they are adhering to RFC 3514 then there won't be any issue. This is what we have standards for.
Tequila: It's not just for breakfast anymore!
This kind of thing is going to be an issue with all signature based AV detection. Changing a few bytes that won't alter the execution of the script/binary will change the signature the AV sees.
In this case it might be fairly easy to program the AVs engine to ignore null bytes in HTML, but how hard would it be to make other minor changes to the code that don't alter the execution but do change the signature. This kind of scanning will only ever catch copy/paste type exploits.
The AV simply doesn't know what bytes are significant, probably inserting a few NOPs or at most recompiling with minor code changes will slip most viri/trojans past signature based scanners, and I don't see how it could really be otherwise without making AV software orders of magnitude more complex and resource hungry than it already is.
You can blame the AV companies, but there's a limit to how effective signature based AVs can be, and using detection based on behavior generally requires the user to know something about what the hell their PC is actually supposed to be doing in the first place, which would make it useless for precisely the users who most need AV protection.
As I'm sure many have said before AV software is a sticking plaster over a gaping wound, if your browser decides to execute untrusted code from the internet with full privileges no amount of AV software out there will save you from getting owned.