February was a particularly busy month for search-based malvertising with the number of incidents we documented almost doubling. We saw similar payloads being dropped but also a few new ones that were particularly good at evading detection.
One malware family we have been tracking on this blog is FakeBat. It is very unique in that the threat actor uses MSI installers packaged with heavily obfuscated PowerShell code. For weeks, the malvertiser helping to distribute this malware was abusing the same URL shortener services which may have made the attack somewhat predictable. We saw them experimenting with new redirectors and in particular leveraging legitimate websites to bypass security checks.
Another interesting aspect is the diversity of the latest campaigns. For a while, we saw the same software brands (Parsec, Freecad) being impersonated over and over again. With this latest wave of FakeBat malvertising, we are seeing many different brands being targeted.
All the incidents described in this blog have been reported to Google.
New redirection chain
During the past several weeks, FakeBat malvertising campaigns used two kinds of ad URLs. As observed in other malvertising campaigns, they were abusing URL/analytics shorteners which are ideal for cloaking. That practice enables a threat actor to use a ‘good’ or ‘bad’ destination URL based on their own defined parameters (time of day, IP address, user-agent, etc.).
The other type of redirect was using subdomains from expired and sitting .com domains reassigned for malicious purposes. This is a common trick to give the illusion of credibility. However, in the most recent malvertising campaigns we see the threat actor abusing legitimate websites that appear to have been compromised.
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