Whoami Process Activity

  1[metadata]
  2creation_date = "2020/02/18"
  3integration = ["endpoint", "system", "windows", "m365_defender"]
  4maturity = "production"
  5updated_date = "2024/06/25"
  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 = ["winlogbeat-*", "logs-endpoint.events.process-*", "logs-windows.*", "logs-system.*", "endgame-*", "logs-m365_defender.event-*"]
 21language = "eql"
 22license = "Elastic License v2"
 23name = "Whoami Process Activity"
 24note = """## Triage and analysis
 25
 26### Investigating Whoami Process Activity
 27
 28After 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.
 29
 30This 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.
 31
 32#### Possible investigation steps
 33
 34- 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.
 35- Identify the user account that performed the action and whether it should perform this kind of action.
 36- Investigate other alerts associated with the user/host during the past 48 hours.
 37- Investigate any abnormal account behavior, such as command executions, file creations or modifications, and network connections.
 38
 39### False positive analysis
 40
 41- 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.
 42
 43### Related rules
 44
 45- Account Discovery Command via SYSTEM Account - 2856446a-34e6-435b-9fb5-f8f040bfa7ed
 46
 47### Response and remediation
 48
 49- Initiate the incident response process based on the outcome of the triage.
 50- Isolate the involved hosts to prevent further post-compromise behavior.
 51- 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.
 52- Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and malware components.
 53- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
 54- 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).
 55"""
 56risk_score = 21
 57rule_id = "ef862985-3f13-4262-a686-5f357bbb9bc2"
 58setup = """## Setup
 59
 60If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2,
 61events will not define `event.ingested` and default fallback for EQL rules was not added until version 8.2.
 62Hence for this rule to work effectively, users will need to add a custom ingest pipeline to populate
 63`event.ingested` to @timestamp.
 64For more details on adding a custom ingest pipeline refer - https://www.elastic.co/guide/en/fleet/current/data-streams-pipeline-tutorial.html
 65"""
 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]
 77timestamp_override = "event.ingested"
 78type = "eql"
 79
 80query = '''
 81process where host.os.type == "windows" and event.type == "start" and process.name : "whoami.exe" and
 82(
 83  (
 84    /* scoped for whoami execution under system privileges */
 85    (
 86      user.domain : ("NT *", "* NT", "IIS APPPOOL") and
 87      user.id : ("S-1-5-18", "S-1-5-19", "S-1-5-20", "S-1-5-82-*") and
 88      not ?winlog.event_data.SubjectUserName : "*$"
 89    ) and
 90    not (
 91      process.parent.name : "cmd.exe" and
 92      process.parent.args : (
 93          "chcp 437>nul 2>&1 & C:\\WINDOWS\\System32\\whoami.exe  /groups",
 94          "chcp 437>nul 2>&1 & %systemroot%\\system32\\whoami /user",
 95          "C:\\WINDOWS\\System32\\whoami.exe /groups",
 96          "*WINDOWS\\system32\\config\\systemprofile*"
 97      )
 98    ) and
 99    not (process.parent.executable : "C:\\Windows\\system32\\inetsrv\\appcmd.exe" and process.parent.args : "LIST") and
100    not process.parent.executable : (
101        "C:\\Program Files\\Microsoft Monitoring Agent\\Agent\\MonitoringHost.exe",
102        "C:\\Program Files\\Cohesity\\cohesity_windows_agent_service.exe"
103    )
104  ) or
105  process.parent.name : ("wsmprovhost.exe", "w3wp.exe", "wmiprvse.exe", "rundll32.exe", "regsvr32.exe")
106)
107'''
108
109
110[[rule.threat]]
111framework = "MITRE ATT&CK"
112[[rule.threat.technique]]
113id = "T1033"
114name = "System Owner/User Discovery"
115reference = "https://attack.mitre.org/techniques/T1033/"
116
117
118[rule.threat.tactic]
119id = "TA0007"
120name = "Discovery"
121reference = "https://attack.mitre.org/tactics/TA0007/"