Recent changes made to the Terror exploit kit (EK) allow it to fingerprint victims and target specific vulnerabilities instead of carpet bombing the victims with many exploits at the same time, Talos researchers discovered.

Terror was initially detailed in January this year, when security researchers observed that it was targeting vulnerabilities with exploits taken from Metasploit or from either Sundown or Hunter EKs. Terror activity increased last month, after the Sundown EK inexplicably disappeared from the threat landscape.

Previously, the EK was observed carpet bombing victims with many exploits at the same time, even if those exploits didn’t match the targeted browser environment. Now, the threat has added more exploits and is fingerprinting victim’s system to determine what exploit would be successful based on operating system, patch level, browser version, and installed plugins.

The use of more targeted exploits makes it more difficult for investigators to determine which exploits the toolkit has. However, “it is interesting to note that the adversaries are using an URL parameter in cleartext for the vulnerability they are going to exploit,” Talos says.

Additionally, Talos researchers identified a potentially compromised legitimate web site that appears to be operating as a malware gate. Initially redirecting visitors to a RIG landing page, the gate switched to Terror after a single day.

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