Malicious software disguised as phony anti-virus programs has been combated for half a decade, which is why attackers now are evading detection by using stolen digital certificates.
The researchers with anti-virus software company Bitdefender recently uncovered a batch of such samples, named Antivirus Security Pro, that have been tweaked to come with the digitally signed installer.
“More to the point, the installer file served via the internet is signed with a digital certificate issued for Ease Entertainment Services, LLC on November 22nd last year,” according to a post by Bogdan Botezatu, senior E-Threat analyst with Bitdefender. “The digital certificate is still valid (it has not been revoked yet). Most likely, it was stolen.”
The Bitdefender team alerted Ease Entertainment Services of the digital theft, so the certificate should be revoked soon, according to Botezatu, who explained that the criminals did not extend the validity of the time-stamp – it expires in November 2014 – because of how quickly compromised certificates are invalidated.
Antivirus Security Pro is a standard scam. Upon download, the bogus program scans systems and then falsely alerts users that their computers are infected with serious malware. Users are then required to pay for the full version in order to remove it.
“Modern operating systems treat digitally signed files differently when they attempt to perform system-wide modifications,” Botezatu wrote. “Prompts of unsigned applications trying to elevate their privileges attract much more user scrutiny than other prompts.”