Old Malware Tricks Still Defeat Most AV Scanners

SkiifGeek writes "A year ago Didier Stevens discovered that padding IE malware with 0x00 bytes would happily slip past most of the scanners in use at VirusTotal.com. Revisiting his earlier discovery, Didier found that detection on his initial samples had improved, but not by much. For all the talk of AV companies moving away from signature based detection to heuristics, it is painfully obvious that not many of the tested engines can successfully handle such a simple and well known obfuscation method and the best of those that can detect the obfuscation can only detect it as a generic malware type. At least the scanning engines that can detect the presence of malware with the obfuscation aren't trying to claim each differential as a new variant."

Comments

Re:uh oh

[noundi]

Your post gave me a thought. How come no AV markets their software using relativity? I mean what use does the average user have for a software that detects a decade old piece of malicous code, that most likely doesn't even work anymore? Perhaps it's time that they market their software with fixes for current problems, not brag about their huge bank of outdated viruses. That creates nothing but a bloated AV, which in the end will most likely hog your system more than it should.

Re:Credit Card Companies

[peragrin]

while you are correct, the problem lies with the OS that needs the most AV support. Windows itself acts like a virus to change memory locations when certian apps are run. Thisis to ensure compatibility. With Vista msft has been trying to change such behaviour, but it took 6years for msft to notice the problem and at least until win7 until things start working better. Linux and OSX don't suffer from such things as badly as they depracrate old buggy features ona regular basis.

Didn't Consumer Reports say this years ago?

[tkrotchko]

A few years back, Consumer Reports took some malware and made some trivial changes and almost all the AV vendors failed that simple test.

If you recall the AV vendors criticized Consumer Reports because they claimed it was the equivalent of producing new malware and that it was irresponsible.

Bottom line... this pretty much proves that AV has little or no value. You use it because everybody tells you that you have to use it, not because it provides any sort of comprehensive security (it doesn't even come close).

Re:Credit Card Companies

[nabsltd]

The thing about anti-virus software is that is stupidly tries not to be intrusive. AV software could be pretty much 100% effective with a few tiny changes, but those changes will make it more visible and annoying.

1. At install, the AV software adds a "run at reboot" entry that runs in the PE boot time, before most (but not all) other processes get a chance to run and does a full system scan at that point. You don't get to continue the install until you agree to this reboot.
2. After the scan, the AV software (still in the PE environment) picks a few select directories (like "C:\Windows" and "C:\Program Files") and creates checksums of all files in those directories (or subdirectories).
3. When the re-boot finishes and the install completes, the user is given the option to add other directories to the "safe" list, and file checksums in those directories are computed.
4. After this, the AV software will not allow a file on disk to be run as an executable unless it is in one of the "safe" directories and the checksum exists and has not changed.
5. Any other attempt to execute a file results in a full scan of the file using the virus signatures, and the user is then given a warning about running non-trusted executable and analysis of the scan.
6. The AV software will provide a way to manually update the "safe" directories, so that after you install software you can run it, but there should be no way to automate it.
7. As an option, the AV software blocks write access to every executable file in the "safe" directories.

This won't protect against scripting language malware and exploits of ActiveX (or other in-process DLL code), but it will tend to stop what they can do in the long run. Exploit code can create an executable in some directory, but it won't be able to be run without a warning, even if that code contains no known virus.

Re:Padding with 0x00 bytes?

[mrops]

Man, Let me tell you, Viruses have evolved. Really evolved. I don't run a anti-virus at home, don't like them.

In a moment of weekness I started watching a downloaded version of stargate, missed it on friday :( the WMV movie asked for a "codec" to be installed, guess what... (I know I should have know better)

Its been 4 weeks and I am still struggling with this virus. Most virus scanners detect this beast, however in my last 4 weeks, none can properly clean it. This has become somewhat of a challenge.

I have discovered so far, that
- it is installed as windows driver,
- this driver gets notified at winlogon
- the driver creates a exe
- the exe executes and stays in memory
- the virus driver file then mutates and goes elsewhere, again to come back at the next logon, this mutation is what virus scanners can't work with.
- Spreads via Windows networking to other computers on the network, this however only if the other computers have any shared writable folders.

Yesterday, I discovered, the crappy thing downloads and installs stuff off the internet.

Fortunately I have all data backed up.

I can re-install my XP anytime, but this has become too challanging to let go.

Here is a kicker, I tried infecting a qemu emulated XP VM, guess what, there is a newer version of the virus, somewhat different than 4 weeks ago. The new codec that downloaded wasn't the same that got downloaded to my machine.

So it seems these virus/trojan developers are well funded and doing this as a day job. Hoping this trojan shares some mp3s so RIAA can go after them, they seem to be more effective than FBI in tracking this kind of a thing.

Here to some good news, my dad's Vista PC is immune to this virus, so Microsoft may have done something right, or maybe the virus/trojan developers are not targeting Vista.

Antivirus/Antispyware 2009

[Danzigism]

Working in a repair shop, the most common infection I've seen in the past couple months has been the rogue antivirus/antispyware products. They usually pose as "Antivirus 2009" or "XP Antivirus 2009". They use extremely generic names. Its funny because every customer that has one of these infections, is usually running Norton, Mcafee, Trend Micro, AVG, or any of them. Not ONE of them from 2008 has been able to rid the rogue product. It's funny too because all you have to do is remove a couple lines in HiJackThis and remove the Program Files folder. Although it has made our repair shop a good amount of money, it is annoying having to tell customers why their AV software can't remove such a silly thing. I've been a strong supporter of Panda Antivirus for many years, and I've always thought all the others are extremely bloated. ESPECIALLY NORTON.. HOWEVER, Norton 2009 has literally done a 180 with its performance. It removed XP Antivirus in no time. It barely uses 1% of your CPU when it is idle, and it updates literally every few minutes. I've been extremely impressed with their latest release and would recommend the noobs out there to try a 15 day free trial. But of course, ultimately running any AV software is a joke if you know how to use your computer correctly and don't download goat pr0n and warez. but fyi, if you would of asked me a month ago about Norton, I would of told you it is ridiculous and extremely bloated crap software, just like the rest.