RIG Exploit Kit Used to Deliver “Cryptowall” Ransomware

The RIG Exploit Kit, which first emerged on cybercrime forums in April, is successfully leveraging malicious advertising techniques (malvertising) to distribute a piece of file-encrypting ransomware dubbed Cryptowall.

According to Cisco, a high amount of traffic associated with the RIG Exploit Kit has been seen using malvertising to perform drive-by download attacks on the visitors of popular, legitimate websites. Cisco said that on April 24 it began to identify malicious traffic related to the attacks, whic so far has been coming from over 90 domains.

According to Cisco, that attacks have been found using landing pages that host exploits for Java, Flash and Silverlight. Cisco researchers highlight the fact that attackers are increasingly using Microsoft Silverlight exploits in their operations, with such exploits being included in packs like Fiesta and Angler as well.

If the exploit is successful, the payload, namely the Cryptowall ransomware, is downloaded onto victims’ computers. Once it infects a system, Cryptowall, which is similar to the notorious CryptoLocker, encrypts local files and instructs users to pay a ransom in order to recover them.

Based on the requests for RIG landing pages, experts have been able to identify the websites hosting the malicious ads. The list of affected sites includes ebay.in, altervista.org, apps.facebook.com, wiki.answers.com, theguardian.com and go.com.  Most of the impacted users are located in the United States (42%) and the United Kingdom (31%).

Until May 22, cybercriminals used both compromised legitimate websites and newly-registered domains to host the landing pages. Many of the hijacked domains are running WordPress, and they’ve been most likely compromised through brute-force attacks, rather than vulnerabilities in the platform, Cisco noted.

“Using existing legitimate sites to host the EK alleviates the need to create and maintain a dedicated domain infrastructure, and mitigates some of the problems associated with doing so: registering new domains, randomizing naming, using multiple email addresses, etc., in order to avoid easy attribution,” Cisco’s Andrew Tsonchev explained in a blog post.

After May 22, only newly-registered domain names have been utilized. Starting with this date, the attackers also stopped using only paths ending in “proxy.php,” most likely in an effort to avoid detection, experts said.

In May, Kahu Security reported that the RIG Exploit Kit was being rented for $60 per day or $300 per week.