SoylentNews

AnonTechie writes:

CryptoWall, one of a family of malware programs that encrypts files and demands a ransom from victims, has undergone a revamp that is frustrating security researchers.

Cisco's Talos Security Intelligence and Research Group has now analyzed a second version of CryptoWall that has improvements that make it harder to detect and study.

The sample of CryptoWall analyzed by Cisco was sent via email in a ".zip" attachment. Contained in that attachment is an exploit that uses a Microsoft privilege escalation vulnerability, CVE-2013-3660 ( http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2013-3660 ), to gain greater control over the computer, Carter said.

If opened, CryptoWall doesn't decrypt its whole binary but instead just a small part, which then checks to see if it is running in a virtual environment, Carter said.

CryptoWall won't continue to decrypt itself if it is running in a virtual machine. Files are sometimes analyzed in a sandbox within a virtual machine to check if they're possibly malicious.

http://www.computerworld.com/article/2865303/cryptowall-ransomware-variant-gets-new-defenses.html

Cisco has a full technical writeup on its blog. http://blogs.cisco.com/security/talos/cryptowall-2