Losing access to VirusTotal Intelligence at the start of the year was surprisingly productive. Unable to hunt for interesting new malware, I stopped adding to my “TODO” pile and finally worked through my backlog from last year. That led to a detailed examination of BeheMOF as well as the discovery of this malware. Upon closer inspection, a sample that did not seem too noteworthy at first turned out to have a distinctive design once I looked under the hood: a passive backdoor that opens no obvious listening port and carries no payload inside itself. It waits in memory doing nothing at all until one specifically crafted network packet reaches the machine, which is why I am calling it SLEEPWALKER.