A newly discovered botnet that appears designed to send spam emails likely infected around 400,000 machines to date, 360 Netlab security researchers warn.
Dubbed BCMPUPnP_Hunter, the threat was observed mainly targeting routers that have the BroadCom UPnP feature enabled. The botnet emerged in September, but a multi-step interaction between the botnet and the potential target prevented the researchers from capturing a sample until last month.
The interaction, 360 Netlab explains, starts with tcp port 5431 destination scan, after which the malware checks the target’s UDP port 1900 and then waits for the proper vulnerable URL. After four other packet exchanges, the attacker finally figures out the shellcode’s execution start address in memory and delivers the proper exploit.