Linux Reverse Shell via Xterm

[rule]
description = """
This rule detects potential reverse shell activity initiated via the xterm terminal emulator. Attackers may use xterm to
establish a reverse shell connection to a remote host by specifying a display address that includes the attacker's IP
and port. This behavior is often indicative of unauthorized remote access attempts.
"""
id = "b364b480-0714-4694-a950-5563dbaae85e"
license = "Elastic License v2"
name = "Linux Reverse Shell via Xterm"
os_list = ["linux"]
reference = ["https://pentestmonkey.net/cheat-sheet/shells/reverse-shell-cheat-sheet"]
version = "1.0.1"

query = '''
sequence by process.entity_id with maxspan=5s
  [process where event.type == "start" and event.action == "exec" and process.name == "xterm" and process.args == "-display" and
   /*
    xterm uses ip:port format, where the port is set to 6000 + display number.
   */
   process.command_line regex """.*[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}:[0-9]{1,3}.*"""
  ]
  [network where event.type == "start" and event.action == "connection_attempted" and process.name == "xterm" and
   /*
    X11 protocol says display is an unsigned 16-bit integer, but Xorg / Xephyr / Xnest impose their own limits
    Most practical servers only accept:
      - 0 ≤ DISPLAY ≤ 63, or
      - 0 ≤ DISPLAY ≤ 255, depending on implementation 
   */
   destination.port >= 6000 and destination.port <= 6999]
'''

min_endpoint_version = "7.15.0"
optional_actions = []
[[actions]]
action = "kill_process"
field = "process.entity_id"
state = 0

[[actions]]
action = "kill_process"
field = "process.entity_id"
state = 1

[[actions]]
action = "kill_process"
field = "process.parent.entity_id"
state = 0

[[actions]]
action = "kill_process"
field = "process.parent.entity_id"
state = 1

[[threat]]
framework = "MITRE ATT&CK"
[[threat.technique]]
id = "T1059"
name = "Command and Scripting Interpreter"
reference = "https://attack.mitre.org/techniques/T1059/"
[[threat.technique.subtechnique]]
id = "T1059.004"
name = "Unix Shell"
reference = "https://attack.mitre.org/techniques/T1059/004/"



[threat.tactic]
id = "TA0002"
name = "Execution"
reference = "https://attack.mitre.org/tactics/TA0002/"
[[threat]]
framework = "MITRE ATT&CK"
[[threat.technique]]
id = "T1071"
name = "Application Layer Protocol"
reference = "https://attack.mitre.org/techniques/T1071/"


[threat.tactic]
id = "TA0011"
name = "Command and Control"
reference = "https://attack.mitre.org/tactics/TA0011/"

[internal]
min_endpoint_version = "7.15.0"