Bisonal main module The DLL (pvcu.dll) is Bisonal malware but using a different cipher for C2 communication that other publicly documented samples. Booz Allen Hamilton in 2014 and AhnLab in 2015 reported on Bisonal using a simple XOR cipher to hide the C2 address strings in the body. The Bisonal sample we observed in this case employs the RC4 cipher with the key “78563412”. To date, all Bisonal samples we have seen using RC4 use this same key. The oldest sample we have dates to 2014, so this variant has been in the wild for several years. For example, the Bisonal malware in 2012 used send() and recv() APIs to communicate with its C2