Suspicious which Enumeration

 1[metadata]
 2creation_date = "2023/08/30"
 3integration = ["endpoint"]
 4maturity = "production"
 5updated_date = "2024/10/17"
 6
 7[rule]
 8author = ["Elastic"]
 9description = """
10This rule monitors for the usage of the which command with an unusual amount of process arguments. Attackers may
11leverage the which command to enumerate the system for useful installed utilities that may be used after compromising a
12system to escalate privileges or move latteraly across the network.
13"""
14from = "now-9m"
15index = ["logs-endpoint.events.*", "endgame-*"]
16language = "eql"
17license = "Elastic License v2"
18name = "Suspicious which Enumeration"
19risk_score = 21
20rule_id = "5b18eef4-842c-4b47-970f-f08d24004bde"
21severity = "low"
22tags = [
23    "Domain: Endpoint",
24    "OS: Linux",
25    "Use Case: Threat Detection",
26    "Tactic: Discovery",
27    "Data Source: Elastic Defend",
28    "Data Source: Elastic Endgame",
29]
30timestamp_override = "event.ingested"
31type = "eql"
32query = '''
33process where host.os.type == "linux" and event.type == "start" and event.action in ("exec", "exec_event") and 
34process.name == "which" and process.args_count >= 10 and not (
35  process.parent.name == "jem" or
36  process.parent.executable like ("/vz/root/*", "/var/lib/docker/*") or
37  process.args == "--tty-only"
38)
39
40/* potential tuning if rule would turn out to be noisy
41and process.args in ("nmap", "nc", "ncat", "netcat", nc.traditional", "gcc", "g++", "socat") and 
42process.parent.name in ("bash", "dash", "ash", "sh", "tcsh", "csh", "zsh", "ksh", "fish")
43*/
44'''
45
46[[rule.threat]]
47framework = "MITRE ATT&CK"
48
49[[rule.threat.technique]]
50id = "T1082"
51name = "System Information Discovery"
52reference = "https://attack.mitre.org/techniques/T1082/"
53
54[rule.threat.tactic]
55id = "TA0007"
56name = "Discovery"
57reference = "https://attack.mitre.org/tactics/TA0007/"