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Can Vawtrak malware block enterprise security software?

Emerging malware, like the Vawtrak banking malware, has the ability to block enterprise antimalware measures. Expert Nick Lewis explains how to mitigate the risk.

I read about a form of malware that is using Windows' own software to block enterprise security software from doing its job. Can you explain how this malware works? What other measures should be put in place if the ones we have can be blocked?

Senior Threat Research Engineer Marilyn Melliang of Trend Micro Inc. wrote a blog post about the malware and its use of Windows software restriction policies (SRP).

This malware, dubbed Vawtrak, is modular malware capable of disabling any antimalware software by using SRP, which minimizes the chances of it being detected and removed.

While this technique is not as common as trying to kill the processes related to antimalware tools that allow them to run effectively, it is potentially more effective. Antimalware tools have built-in defenses to prevent an attacker from just killing application processes, deleting files or uninstalling software. While using SRP to disable antimalware is difficult -- it would require correctly configuring the policy to block any potential antimalware tool -- Vawtrak uses an initial downloader to get onto the system and execute the malicious code to infect it.

Vawtrak uses Windows SRP to try to disable 53 different antimalware tools. By putting the path to the executable files used by the antimalware tools into a SRP list, Vawtrak prevents them from running on the system, and therefore disables the antimalware tool.

Generally, traditional endpoint antimalware troubleshooting doesn't look into the SRP configuration. However, starting a system from safe mode or connecting the infected hard drive to a known secure system with updated antimalware definitions could potentially remove the malware.

Enterprises can use the same steps that protect endpoints from malware to protect against Vawtrak, but should verify that the tools can detect it and other malware that is attempting to make changes to SRP or other whitelisting tools. Host-based intrusion detection tools that monitor for host-based changes could also detect the changes from Vawtrak.

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This was last published in February 2015

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