A group of researchers and security firms led by RSA delivered a significant blow to the infrastructure used by the notorious RIG exploit kit and the operation has allowed experts to learn more about the threat.
RSA announced the results of the operation, which it has dubbed “Shadowfall,” on Monday. Several independent researchers and employees of Malwarebytes, Palo Alto Networks and Broad Analysis have contributed to the project.
Following the disappearance of Angler, RIG managed to secure the top position in the exploit kit market, being used to deliver various pieces of malware, including Cerber and CryptoMix ransomware, and the SmokeLoader backdoor. RIG has leveraged several Flash Player, Silverlight, Internet Explorer and Microsoft Edge exploits, which it mainly delivers by injecting malicious iframes into compromised websites.
One important component of RIG attacks is domain shadowing, a technique where attackers steal credentials from domain owners and use them to create subdomains that point to malicious servers. In the case of RIG, researchers identified tens of thousands of shadow domains. An analysis of whois data for these shadow domains showed that many of them had been registered with Internet giant GoDaddy.
With the aid of GoDaddy, tens of thousands of malicious domains were removed in mid-May, striking a significant blow to RIG, particularly a couple of recent campaigns dubbed “Seamless” and “Decimal IP.” However, RSA pointed out that assessing the impact of takedown operations is not an easy task, especially in this case due to the numerous malware campaigns and limited visibility into the threat actor’s activity.
The researchers involved in the operation reported that the exploit kit continued to be active, but noted that it had stopped using Flash Player exploits for a few days. Experts noticed on Monday that RIG had resumed the use of Flash exploits.
As for how attackers managed to hijack the accounts used to create shadow domains, RSA has determined that the compromised credentials don’t appear to come from Pony dumps – the Pony trojan has been used in the past years to steal millions of account credentials.
“In terms of the shadow domains themselves, it is believed that the threat actors waging these campaigns rely upon sophisticated phishing operations to acquire legitimate customer credentials,” RSA said in a blog post. “In terms of the compromised sites, the cross section of affected domain registrars implies a more opportunistic approach. While it remains unclear what methods may have been employed as a means for harvesting these credentials, community research exists on the usage of IoT botnets to brute force WordPress sites.”