Trickbot Svchost.exe Reconn Commands

https://www.vkremez.com/2018/04/lets-learn-trickbot-implements-network.html

Vitali and others have noted that trickbot is running reconn commands. I finally saw them in action and these happen to be children of svchost so I did a quick sig and it looks pretty reliable and quiet. Nothing fancy, just looking for cmd.exe as a child of svchost.exe with common reconn command lines.



Using stats to group the command lines for visibility



Previously I had done something more complex based on the JPCERT analysis to detect reconn more generally.

 https://blogs.jpcert.or.jp/en/2016/01/windows-commands-abused-by-attackers.html

@Cyb3rops did this in a very similar manner way before I did.
https://github.com/Neo23x0/sigma/blob/master/rules/windows/process_creation/win_susp_commands_recon_activity.yml




The eval command_length is a filter for long line junk. The only clever bit is the distinct count of command_lines in order to put a low end threshold for unique commands and the overall counter for total hits. This is a bit slow and noisy but I think is a good signature to have.

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