The developers of the RIG exploit kit appear to be testing new infection methods and a different type of URL pattern for command and control (C&C) communications that could help the threat evade detection.
RIG, one of the exploit kits that replaced Angler after its demise, has been using Flash exploits to infect computers with malware. However, on August 20 and August 21, researchers at Cyphort spotted a new build that included several other exploits as well. The new variant was only seen for two days, which led experts to believe that cybercriminals might have only conducted some tests.
The new version of RIG used several old and newer exploits targeting Microsoft products. One of them targets CVE-2016-0189, a remote code execution vulnerability in the JScript and VBScript scripting engines used in Windows. The flaw, which Microsoft patched in May, can be exploited through the Internet Explorer web browser.
A proof-of-concept (PoC) for CVE-2016-0189 was released by researchers on June 22 and, a few weeks later, it was adapted by cybercriminals and added to the Neutrino exploit kit. RIG developers are apparently also working on integrating it into their creation.
Another exploit spotted in the new RIG build was for CVE-2013-2551, a use-after-free vulnerability in Internet Explorer that was disclosed by VUPEN researchers in 2013. The flaw has been exploited in numerous attacks over the past years, including by the Neutrino exploit kit.
Experts also noticed that RIG had leveraged an exploit for CVE-2014-6332, a Windows OLE vulnerability that can be used for remote code execution via Internet Explorer. This security hole has also been used by Neutrino, but it has also been observed in more sophisticated APT campaigns.
Cyphort also discovered the use of a Silverlight exploit and pointed out that this was the first time RIG leveraged Silverlight flaws to infect victims.
In addition to the new exploits, the latest RIG build makes some changes to the C&C communication method used in the last couple of months. The URL patterns used until now have been relatively predictable, allowing security solutions to easily block the threat. However, RIG developers have been testing new patterns that could help their creation avoid easy detection.
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