Linux Restricted Shell Breakout via cpulimit Shell Evasion

 1[metadata]
 2creation_date = "2022/03/17"
 3deprecation_date = "2022/05/09"
 4maturity = "deprecated"
 5updated_date = "2022/05/09"
 6
 7[rule]
 8author = ["Elastic"]
 9description = """
10Identifies Linux binary cpulimit abuse to break out from restricted environments by spawning an interactive system
11shell. The cpulimit utility is used to restrict the CPU usage of a process in cases of CPU or system load exceeding the
12defined threshold and the activity of spawning a shell is not a standard use of this binary by a user or system
13administrator. This can potentially indicate a malicious actor attempting to improve the capabilities or stability of
14their access.
15"""
16from = "now-9m"
17index = ["logs-endpoint.events.*"]
18language = "eql"
19license = "Elastic License v2"
20name = "Linux Restricted Shell Breakout via cpulimit Shell Evasion"
21references = ["https://gtfobins.github.io/gtfobins/cpulimit/"]
22risk_score = 47
23rule_id = "0968cfbd-40f0-4b1c-b7b1-a60736c7b241"
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 in ("bash", "sh", "dash") and
31  process.parent.name == "cpulimit" and process.parent.args == "-f" and
32  process.parent.args in ("/bin/sh", "/bin/bash", "/bin/dash", "sh", "bash", "dash")
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/"