RIG has been the top exploit kit since Angler was taken down, delivering both Cerber and CryptoMix ransomwares as well as the SmokeLoader backdoor. Typically, it inserts fake iframes into compromised WordPress, Joomla and Drupal sites. These cause victim browsers to land on attacker-controlled webpages.
RIG uses Domain shadowing as one of its main characteristics. This method occurs when attackers steal actual credentials from domain owners and then use them to create subdomains pointing to malicious servers. These malicious servers hide in legitimate domains, making them unlikely to be blacklisted simply because of the suspicion of malfeasance.
According to RSA, the “shadowing activity was observed in over 30,000 subdomains total affecting over 800 domains. The active subdomains were constantly fluctuating with entries continually being added and removed in an automated fashion with an average of 900 record modifications per day.” These subdomains are short-lived, typically only existing for 24 to 48 hours.
Using the Exploit Kit’s Common Link
The domains did contain one common link: They had a high incidence of being registered by GoDaddy, one of the biggest registrars on the internet. RSA enlisted GoDaddy’s help in the project, and they worked together to identify malware-used domains.
How the threat actors actually obtain the credentials for the domains is still somewhat opaque. There have been some data dumps in the past, but RSA suggested that there was anecdotal evidence pointing to usage of Internet of Things (IoT) botnets to brute force WordPress sites, along with the use of sophisticated spear fishing campaigns.
With GoDaddy’s aid, the groups managed to remove thousands of active shadow domain resources through revocation. This action undoubtedly put a crimp into RIG’s operation, but even RSA wondered how long such an action will last. As it explained, “Determining the impact of such a takedown on the inextricable pile of ongoing ransomware, malvertising and malspam campaigns is significantly more challenging.”