Microsoft’s Patch Tuesday for October fixed another previous zero-day vulnerability in Internet Explorer (IE) via MS16-118 and MS16-126: CVE-2016-3298. Before the lid was put on it, the security flaw was employed alongside CVE-2016-3351 by operators of the AdGholas malvertising campaign, analysis and disclosure of which were made with our collaboration with Proofpoint’s @kafeine last July 2016. The campaign was notable for the economies of scale and scope it achieved in its heyday until its operations were stymied. As shared by @kafeine, it was even integrated in Neutrino exploit kit’s malvertising chain as a malicious JavaScript.

Exploiting CVE-2016-3298 enables attackers to check for specific antivirus (AV) software installed in the system in order to avoid AV detection and threat research/analysis. This sounds innocuous, but determining if the system is unsecure eases—and even automates—the undertaking of sneaking malware into it.