Whoami Process Activity

  1[metadata]
  2creation_date = "2020/02/18"
  3integration = ["endpoint", "system", "windows", "m365_defender"]
  4maturity = "production"
  5updated_date = "2025/03/20"
  6
  7[rule]
  8author = ["Elastic"]
  9description = """
 10Identifies suspicious use of whoami.exe which displays user, group, and privileges information for the user who is
 11currently logged on to the local system.
 12"""
 13false_positives = [
 14    """
 15    Some normal use of this program, at varying levels of frequency, may originate from scripts, automation tools and
 16    frameworks. Usage by non-engineers and ordinary users is unusual.
 17    """,
 18]
 19from = "now-9m"
 20index = [
 21    "endgame-*",
 22    "logs-endpoint.events.process-*",
 23    "logs-m365_defender.event-*",
 24    "logs-system.security*",
 25    "logs-windows.forwarded*",
 26    "logs-windows.sysmon_operational-*",
 27    "winlogbeat-*",
 28]
 29language = "eql"
 30license = "Elastic License v2"
 31name = "Whoami Process Activity"
 32note = """## Triage and analysis
 33
 34### Investigating Whoami Process Activity
 35
 36After successfully compromising an environment, attackers may try to gain situational awareness to plan their next steps. This can happen by running commands to enumerate network resources, users, connections, files, and installed security software.
 37
 38This rule looks for the execution of the `whoami` utility. Attackers commonly use this utility to measure their current privileges, discover the current user, determine if a privilege escalation was successful, etc.
 39
 40#### Possible investigation steps
 41
 42- Investigate the process execution chain (parent process tree) for unknown processes. Examine their executable files for prevalence, whether they are located in expected locations, and if they are signed with valid digital signatures.
 43- Identify the user account that performed the action and whether it should perform this kind of action.
 44- Investigate other alerts associated with the user/host during the past 48 hours.
 45- Investigate any abnormal account behavior, such as command executions, file creations or modifications, and network connections.
 46
 47### False positive analysis
 48
 49- Discovery activities are not inherently malicious if they occur in isolation. As long as the analyst did not identify suspicious activity related to the user or host, such alerts can be dismissed.
 50
 51### Related rules
 52
 53- Account Discovery Command via SYSTEM Account - 2856446a-34e6-435b-9fb5-f8f040bfa7ed
 54
 55### Response and remediation
 56
 57- Initiate the incident response process based on the outcome of the triage.
 58- Isolate the involved hosts to prevent further post-compromise behavior.
 59- Investigate credential exposure on systems compromised or used by the attacker to ensure all compromised accounts are identified. Reset passwords for these accounts and other potentially compromised credentials, such as email, business systems, and web services.
 60- Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and malware components.
 61- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
 62- Using the incident response data, update logging and audit policies to improve the mean time to detect (MTTD) and the mean time to respond (MTTR).
 63"""
 64risk_score = 21
 65rule_id = "ef862985-3f13-4262-a686-5f357bbb9bc2"
 66severity = "low"
 67tags = [
 68    "Domain: Endpoint",
 69    "OS: Windows",
 70    "Use Case: Threat Detection",
 71    "Tactic: Discovery",
 72    "Resources: Investigation Guide",
 73    "Data Source: Elastic Endgame",
 74    "Data Source: Elastic Defend",
 75    "Data Source: Microsoft Defender for Endpoint",
 76    "Data Source: Sysmon",
 77    "Data Source: Windows Security Event Logs",
 78]
 79timestamp_override = "event.ingested"
 80type = "eql"
 81
 82query = '''
 83process where host.os.type == "windows" and event.type == "start" and process.name : "whoami.exe" and
 84(
 85  (
 86    /* scoped for whoami execution under system privileges */
 87    (
 88      (
 89        user.domain : ("NT *", "* NT", "IIS APPPOOL") and
 90        user.id : ("S-1-5-18", "S-1-5-19", "S-1-5-20", "S-1-5-82-*") and
 91        not ?winlog.event_data.SubjectUserName : "*$" and
 92
 93        /* Sysmon will always populate user.id as S-1-5-18, leading to FPs */
 94        not event.dataset : ("windows.sysmon_operational", "windows.sysmon")
 95      ) or
 96      (?process.Ext.token.integrity_level_name : "System" or ?winlog.event_data.IntegrityLevel : "System")
 97    ) and
 98    not (
 99      process.parent.name : "cmd.exe" and
100      process.parent.args : (
101          "chcp 437>nul 2>&1 & C:\\WINDOWS\\System32\\whoami.exe  /groups",
102          "chcp 437>nul 2>&1 & %systemroot%\\system32\\whoami /user",
103          "C:\\WINDOWS\\System32\\whoami.exe /groups",
104          "*WINDOWS\\system32\\config\\systemprofile*"
105      )
106    ) and
107    not (process.parent.executable : "C:\\Windows\\system32\\inetsrv\\appcmd.exe" and process.parent.args : "LIST") and
108    not process.parent.executable : (
109        "C:\\Program Files\\Microsoft Monitoring Agent\\Agent\\MonitoringHost.exe",
110        "C:\\Program Files\\Cohesity\\cohesity_windows_agent_service.exe"
111    )
112  ) or
113  process.parent.name : ("wsmprovhost.exe", "w3wp.exe", "wmiprvse.exe", "rundll32.exe", "regsvr32.exe")
114)
115'''
116
117
118[[rule.threat]]
119framework = "MITRE ATT&CK"
120[[rule.threat.technique]]
121id = "T1033"
122name = "System Owner/User Discovery"
123reference = "https://attack.mitre.org/techniques/T1033/"
124
125
126[rule.threat.tactic]
127id = "TA0007"
128name = "Discovery"
129reference = "https://attack.mitre.org/tactics/TA0007/"