Elastic Defend high stable eql

Linux Reverse Shell

Detects the creation of a reverse shell through a suspicious parent child relationship spawned via a shell with suspicious command line arguments. Attackers may spawn reverse shells to establish persistence onto a target system.

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Detection Logic

sequence with maxspan=5s
  [network where event.type == "start" and event.action in ("connection_attempted", "connection_accepted") and 
   process.name in ("bash", "dash", "sh", "tcsh", "csh", "zsh", "ksh", "fish", "socat") and 
   not (destination.ip == null or destination.ip == "0.0.0.0" or cidrmatch(
     destination.ip, "10.0.0.0/8", "127.0.0.0/8", "169.254.0.0/16", "172.16.0.0/12", "192.0.0.0/24", "192.0.0.0/29",
     "192.0.0.8/32", "192.0.0.9/32", "192.0.0.10/32", "192.0.0.170/32", "192.0.0.171/32", "192.0.2.0/24",
     "192.31.196.0/24", "192.52.193.0/24", "192.168.0.0/16", "192.88.99.0/24", "224.0.0.0/4", "100.64.0.0/10",
     "192.175.48.0/24","198.18.0.0/15", "198.51.100.0/24", "203.0.113.0/24", "240.0.0.0/4", "::1", "FE80::/10",
     "FF00::/8"
     )
   )] by process.entity_id
  [process where event.type == "start" and event.action in ("exec", "fork") and 
   process.name in ("bash", "dash", "sh", "tcsh", "csh", "zsh", "ksh", "fish") and (
     (process.args in ("-i", "-il", "-li")) or (process.parent.name == "socat" and process.parent.command_line like~ "*exec*")
   )] by process.parent.entity_id

Field Validations

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