The RIG Exploit Kit is using malicious advertising techniques to distribute a piece of file-encrypting ransomware called Cryptowall.
The kit first gained visibility in April, said researchers at Cisco. In addition, there was a high amount of traffic associated with the RIG Exploit Kit which uses malvertising to perform drive-by download attacks on the visitors of popular, legitimate websites.
Cisco said it began to identify malicious traffic related to the attacks on April 24, which so far has been coming from over 90 domains.
Attacks use landing pages that host exploits for Java, Flash and Silverlight, Cisco researchers said.
Attackers are increasingly using Microsoft Silverlight exploits in their operations, with such exploits being included in packs like Fiesta and Angler as well, the researchers said.
If the exploit is successful, the payload, namely the Cryptowall ransomware, downloads 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. Most of the users suffering an impact are from the United States (42 percent) and the United Kingdom (31 percent).
Until May 22, cybercriminals used compromised legitimate websites and newly-registered domains to host the landing pages. Many of the hijacked domains are running WordPress, and most likely they ended up compromised through brute-force attacks, rather than vulnerabilities in the platform, Cisco said.
“Using existing legitimate sites to host the (exploit kit) 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,” said Cisco’s Andrew Tsonchev in a blog.
After May 22, only newly-registered domain names were seeing use. Starting with this date, the attackers also stopped using only paths ending in “proxy.php,” most likely in an effort to avoid detection, researchers said.