Linux Restricted Shell Breakout via the SSH command

 1[metadata]
 2creation_date = "2022/03/10"
 3deprecation_date = "2022/05/09"
 4maturity = "deprecated"
 5updated_date = "2022/05/09"
 6
 7[rule]
 8author = ["Elastic"]
 9description = """
10Identifies Linux binary SSH abuse to break out from restricted environments by spawning an interactive system shell. The
11SSH protocol is a network protocol that gives users, particularly system administrators, a secure way to access a
12computer over a network. The activity of spawning shell is not a standard use of this binary for a user or system
13administrator. It indicates a potentially malicious actor attempting to improve the capabilities or stability of their
14access.
15"""
16from = "now-9m"
17index = ["logs-endpoint.events.*"]
18language = "eql"
19license = "Elastic License v2"
20name = "Linux Restricted Shell Breakout via the SSH command"
21references = ["https://gtfobins.github.io/gtfobins/ssh/"]
22risk_score = 47
23rule_id = "97da359b-2b61-4a40-b2e4-8fc48cf7a294"
24severity = "medium"
25tags = ["Elastic", "Host", "Linux", "Threat Detection", "Execution", "GTFOBins"]
26timestamp_override = "event.ingested"
27type = "eql"
28
29query = '''
30process where event.type == "start" and process.name : ("bash", "sh", "dash") and
31  process.parent.name == "ssh" and process.parent.args == "-o" and
32  process.parent.args in ("ProxyCommand=;sh 0<&2 1>&2", "ProxyCommand=;bash 0<&2 1>&2", "ProxyCommand=;dash 0<&2 1>&2", "ProxyCommand=;/bin/sh 0<&2 1>&2", "ProxyCommand=;/bin/bash 0<&2 1>&2", "ProxyCommand=;/bin/dash 0<&2 1>&2")
33'''
34
35
36[[rule.threat]]
37framework = "MITRE ATT&CK"
38[[rule.threat.technique]]
39id = "T1059"
40name = "Command and Scripting Interpreter"
41reference = "https://attack.mitre.org/techniques/T1059/"
42[[rule.threat.technique.subtechnique]]
43id = "T1059.004"
44name = "Unix Shell"
45reference = "https://attack.mitre.org/techniques/T1059/004/"
46
47
48
49[rule.threat.tactic]
50id = "TA0002"
51name = "Execution"
52reference = "https://attack.mitre.org/tactics/TA0002/"