PowerShell Suspicious Discovery Related Windows API Functionsedit

This rule detects the use of discovery-related Windows API functions in PowerShell Scripts. Attackers can use these functions to perform various situational awareness related activities, like enumerating users, shares, sessions, domain trusts, groups, etc.

Rule type: query

Rule indices:

  • winlogbeat-*
  • logs-windows.*

Severity: medium

Risk score: 47

Runs every: 5 minutes

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

Tags:

  • Elastic
  • Host
  • Windows
  • Threat Detection
  • Discovery
  • Investigation Guide

Version: 102 (version history)

Added (Elastic Stack release): 7.16.0

Last modified (Elastic Stack release): 8.6.0

Rule authors: Elastic

Rule license: Elastic License v2

Potential false positivesedit

Legitimate PowerShell scripts that make use of these functions.

Investigation guideedit

## Triage and analysis

### Investigating PowerShell Suspicious Discovery Related Windows API Functions

PowerShell is one of the main tools system administrators use for automation, report routines, and other tasks. This
makes it available for use in various environments, and creates an attractive way for attackers to execute code.

Attackers can use PowerShell to interact with the Win32 API to bypass command line based detections, using libraries
like PSReflect or Get-ProcAddress Cmdlet.

#### Possible investigation steps

- Examine the script content that triggered the detection; look for suspicious DLL imports, collection or exfiltration
capabilities, suspicious functions, encoded or compressed data, and other potentially malicious characteristics.
- Investigate the script 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.
- Examine file or network events from the involved PowerShell process for suspicious behavior.
- Investigate other alerts associated with the user/host during the past 48 hours.
- Evaluate whether the user needs to use PowerShell to complete tasks.
- Check for additional PowerShell and command-line logs that indicate that imported functions were run.

### False positive analysis

- Discovery activities themselves are not inherently malicious if occurring in isolation, as long as the script does not
contain other capabilities, and there are no other alerts related to the user or host; such alerts can be dismissed.
However, analysts should keep in mind that this is not a common way of getting information, making it suspicious.

### Related rules

- PowerShell PSReflect Script - 56f2e9b5-4803-4e44-a0a4-a52dc79d57fe

### Response and remediation

- Initiate the incident response process based on the outcome of the triage.
- Isolate the involved hosts to prevent further post-compromise behavior.
- Restrict PowerShell usage outside of IT and engineering business units using GPOs, AppLocker, Intune, or similar software.
- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
- Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and
malware components.
- 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).

Rule queryedit

event.category:process and powershell.file.script_block_text : (
NetShareEnum or NetWkstaUserEnum or NetSessionEnum or
NetLocalGroupEnum or NetLocalGroupGetMembers or DsGetSiteName
or DsEnumerateDomainTrusts or WTSEnumerateSessionsEx or
WTSQuerySessionInformation or LsaGetLogonSessionData or
QueryServiceObjectSecurity )

Threat mappingedit

Framework: MITRE ATT&CKTM

Rule version historyedit

Version 102 (8.6.0 release)
  • Formatting only
Version 101 (8.5.0 release)
  • Formatting only
Version 8 (8.4.0 release)
  • Updated query, changed from:

    event.category:process and powershell.file.script_block_text : (
    NetShareEnum or NetWkstaUserEnum or NetSessionEnum or
    NetLocalGroupEnum or NetLocalGroupGetMembers or DsGetSiteName
    or DsEnumerateDomainTrusts or WTSEnumerateSessionsEx or
    WTSQuerySessionInformation or LsaGetLogonSessionData or
    QueryServiceObjectSecurity )
Version 6 (8.3.0 release)
  • Formatting only
Version 5 (8.2.0 release)
  • Formatting only
Version 4 (8.1.0 release)
  • Formatting only
Version 3 (8.0.0 release)
  • Updated query, changed from:

    event.code:"4104" and powershell.file.script_block_text : (
    NetShareEnum or NetWkstaUserEnum or NetSessionEnum or
    NetLocalGroupEnum or NetLocalGroupGetMembers or DsGetSiteName
    or DsEnumerateDomainTrusts or WTSEnumerateSessionsEx or
    WTSQuerySessionInformation or LsaGetLogonSessionData or
    QueryServiceObjectSecurity )