Analysis and Write-up by Hasherezade.
Intro Excerpt from the Malware-Bytes Analysis Page :
Recently, we described an unusual Chinese drive-by attack that was delivering a variant of the Avzhan DDoS bot. The attack also contained multiple components that were not-so-new. Among the exploits, the newest was from 2016. Avzhan is also not a recent malware—the compilation timestamp of the unpacked payload was from August 2015. But there was one more unusual thing that triggered our attention. The outer layer of Avzhan matched the signatures of Virut, a malware that’s been dead in the water since 2013.
At first, it was hard to believe this detection. Who would want to distribute such an old piece of malware that is no longer developed, and whose CnC servers were sinkholed long ago by Polish CERT? Maybe it was the author of the packer by which the DDoS bot was wrapped incorporating some Virut-like obfuscation?
After further research, it turned out the detection was not wrong. The Avzhan bot carried along with it a legitimate Virut. But it is unlikely that the distributors added it intentionally. Rather, the server from where the attack was deployed happened to be infected with Virut. The virus attached as a parasite to the distributed DDoS malware, and was dropped with the drive-by attack into new places. Interestingly, in 2016 Virut’s code was also found in Chinese cameras. Similarly, the computers of developers were infected with Virut, and by this way its code got passed further.