Trojan patches library code to avoid detection

Powered by SC Magazine
 

Used for long-term data siphoning.

Researchers have discovered a dropper trojan that uses a new trick to stay active but hidden as it takes advantage of vulnerabilities in Windows code.

An analysis from BitDefender researchers revealed the approach of this new trojan.

Rather than acting like traditional malware, Trojan.Dropper.UAJ differs in infecting computers by patching the library file, comres.dll, which forces all applications that rely on it to execute the threat.

Trojans typically add themselves to the start-up registry key, which makes them easy to detect by anti-virus solutions and astute users.

However, this particular trojan makes a copy of the comres.dll file, patches it, then saves it to the Windows directory folder.

“DLL files are generally highly sensitive and need to have the right version and they have to be compiled either for 32- or 64-bit platforms in order to continue working after they have been compromised,” Bogdan Botezatu, e-threats analysis and communications specialist at BitDefender, told SC Magazine in an email.

“This trojan simply patches the right file in order to ensure the DLL file stays compatible with the applications using it.”

The file then opens a backdoor to the infected system, giving the attacker access to carry out administrative actions on the PC. These include adding and removing users, changing user passwords, and running code.

“Although the modus operandi of this dropper is typical to all droppers, this particular take of patching a DLL file makes it rather unique,” Botezatu said.

“We have seen just one similar approach, also targeting comres.dll, in 2010, in a variant of Trojan.PWS.OnlineGames.”

Dropper trojans traditionally infect systems through malicious email attachments that users click on, or via drive-by downloads, by which machines are infected simply by a user surfing to a tainted website, he said.

This trojan is a classic example of malware designed to conduct long-term information siphoning.

“Cyber crooks are working hard to ensure that their creations stay undetected for as long as possible,” he said.

“Although DLL patching is highly unlikely to be perfected further, malware creators will definitely upgrade the payloads.”

This article originally appeared at scmagazineus.com

Copyright © SC Magazine, US edition


Trojan patches library code to avoid detection
 
 
 
Top Stories
ANZ looks to life beyond the transaction
If digital disruptors think an online payments startup could rock the big four, they’ve missed the point of why people use banks, says Patrick Maes.
 
What InfoSec can learn from the insurance industry
[Blog post] Another way data breach laws could help manage risk.
 
A ten-point plan for disrupting security
[Blog post] How can you defend the perimeter when it’s in the cloud?
 
 
Sign up to receive iTnews email bulletins
   FOLLOW US...
Latest Comments
Polls
What is delaying adoption of public cloud in your organisation?







   |   View results
Lock-in concerns
  29%
 
Application integration concerns
  3%
 
Security and compliance concerns
  27%
 
Unreliable network infrastructure
  9%
 
Data sovereignty concerns
  21%
 
Lack of stakeholder support
  3%
 
Protecting on-premise IT jobs
  4%
 
Difficulty transitioning CapEx budget into OpEx
  3%
TOTAL VOTES: 1038

Vote