Stolen digital certificates

March 17th, 2012 by Stephen Jones Leave a reply »

Security companies have recently identified multiple malware threats that use stolen digital certificates to sign their components to avoid detection and bypass Windows defenses.

In 2010, the Stuxnet industrial sabotage worm surprised the security industry with its use of rootkit components that were digitally signed with certificates stolen from semiconductor manufacturers Realtek and JMicron.

A backdoor discovered by Symantec in December installed a rootkit driver signed with a digital certificate stolen from an undisclosed company

If Microsoft were to block the loading of all known files signed with that certificate, probably millions of users of  hardware from around the world would find their motherboards, network cards, etc. inoperable. Therefore, Microsoft cannot block the execution or loading of files signed with stolen certificates.

A malware component identified by Kaspersky Lab researchers during the last few days was signed with a certificate stolen from a Swiss company called Conpavi AG. “The company is known to work with Swiss government agencies such as municipalities and cantons . The threat is detected as Trojan-Dropper.Win32/Win64.Mediyes and is part of a click fraud scheme. However, the signed component is not a driver, but is the actual malware installer, also known as the dropper.

Malware authors are interested in signing installers and not just the drivers, because some antivirus solutions assume that digitally signed files are legitimate and don’t scan them, said Bogdan Botezatu, a senior e-threat analyst at antivirus vendor BitDefender.

Signed modules are more likely to be included in whitelisting collections meaning, the chance of them being fully analyzed is lower and they remain undetected for longer period of times.

Kaspersky Lab and BitDefender have confirmed seeing a steady increase in the number of malware threats with digitally signed components during the last 24 months. Many use digital certificates bought with fake identities, but the use of stolen certificates is also common,

http://www.infoworld.com/d/security/digitally-signed-malware-increasingly-prevalent-researchers-say-188792?page=0,1

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