...Security experts are warning of never-before-seen malware, dubbed Stuxnet, that spreads via USB drives, infecting PCs via an unknown -- aka zero-day -- Windows vulnerability. Unfortunately, the attack works even with AutoRun and AutoPlay disabled, and affects at least Windows 7 Enterprise Edition x86 operating systems......
.........Interestingly, the DLL is disguised as a device driver, which is what allows it to auto-load, thanks to the malware having a valid digital signature from Realtek Semiconductor, a legitimate company. Security researchers are anxious to learn how attackers got their hands on the digital signature, since such signatures are critical for differentiating good software from bad.
As that suggests, "digitally signed malware is a nightmare for antivirus developers," said Aleks Gostev, a security expert at antivirus vendor Kaspersky Lab, in a blog post.
Patching the vulnerability or vulnerabilities exploited by Stuxnet will likely require an operating system fix from Microsoft, rather than simply recalling Realtek's digital signature. "Recalling a certificate from a company like this simply isn't feasible -- it would cause an enormous amount of the software which they've released to become unusable," said Gostev. ........
Stuxnet uses the aforementioned .lnk technique to install additional malware components. It first injects a backdoor (Worm:Win32/Stuxnet.A) onto the compromised system, and then drops two drivers:
* Trojan:WinNT/Stuxnet.A - hides the presence of the .lnk files
* Trojan:WinNT/Stuxnet.B - injects (formerly) encrypted data blobs (.tmp files) into memory, each of which appear to serve different purposes as the Stuxnet deployment system infrastructure (drivers, .lnk files, propagation, etc.).
These drivers are signed with a digital certificate belonging to a well-known hardware manufacturer called Realtek Semiconductor Corp., which is unusual because it would imply that the malware authors somehow had access to Realtek’s private key. Microsoft MMPC has been working with Verisign to revoke this certificate, and did so at 08:05:42 PM UTC with the agreement and support of Realtek.
Edited by buddy215, 17 July 2010 - 07:11 AM.