LoFP LoFP / some normal use of this program, at varying levels of frequency, may originate from scripts, automation tools and frameworks. usage by non-engineers and ordinary users is unusual.

Techniques

Sample rules

Whoami Process Activity

Description

Identifies suspicious use of whoami.exe which displays user, group, and privileges information for the user who is currently logged on to the local system.

Detection logic

process where host.os.type == "windows" and event.type == "start" and process.name : "whoami.exe" and
(
  /* Suspicious parent processes */
  process.parent.name : (
    "wsmprovhost.exe", "w3wp.exe", "wmiprvse.exe", "rundll32.exe", "regsvr32.exe"
  ) or

  /* whoami execution under system privileges */
  (
    (
      (?process.Ext.token.integrity_level_name : "System" or ?winlog.event_data.IntegrityLevel : "System") or
      (
        user.domain : ("NT *", "* NT", "IIS APPPOOL") and
        user.id : ("S-1-5-18", "S-1-5-19", "S-1-5-20", "S-1-5-82-*") and
        not (?winlog.event_data.SubjectUserName : "*$" and ?winlog.event_data.SubjectUserName != null) and

        /* Sysmon will always populate user.id as S-1-5-18, leading to FPs */
        not data_stream.dataset : ("windows.sysmon_operational", "windows.sysmon")
      )
    ) and
    not (
      (
        process.parent.name : "cmd.exe" and
        ?process.parent.args : (
          "chcp 437>nul 2>&1 & C:\\WINDOWS\\System32\\whoami.exe  /groups",
          "chcp 437>nul 2>&1 & %systemroot%\\system32\\whoami /user",
          "C:\\WINDOWS\\System32\\whoami.exe /groups",
          "*WINDOWS\\system32\\config\\systemprofile*"
        )
      ) or
      (
        process.parent.executable : "C:\\Windows\\system32\\inetsrv\\appcmd.exe" and
        ?process.parent.args : "LIST"
      ) or
      (
        process.parent.executable : (
          "C:\\Program Files\\Microsoft Monitoring Agent\\Agent\\MonitoringHost.exe",
          "C:\\Program Files\\Cohesity\\cohesity_windows_agent_service.exe"
        )
      )
    )
  )
)