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Elastic Docs ›Elastic Security Solution [8.15] ›Detections and alerts ›Prebuilt rule reference

PowerShell Keylogging Script

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PowerShell Keylogging Script

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Detects the use of Win32 API Functions that can be used to capture user keystrokes in PowerShell scripts. Attackers use this technique to capture user input, looking for credentials and/or other valuable data.

Rule type: query

Rule indices:

  • winlogbeat-*
  • logs-windows.powershell*

Severity: high

Risk score: 73

Runs every: 5m

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

Maximum alerts per execution: 100

References:

Tags:

  • Domain: Endpoint
  • OS: Windows
  • Use Case: Threat Detection
  • Tactic: Collection
  • Resources: Investigation Guide
  • Data Source: PowerShell Logs

Version: 215

Rule authors:

  • Elastic

Rule license: Elastic License v2

Investigation guide

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Triage and analysis

Investigating PowerShell Keylogging Script

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 abuse PowerShell capabilities to capture user keystrokes with the goal of stealing credentials and other valuable information as credit card data and confidential conversations.

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.
  • Determine whether the script stores the captured data locally.
  • Investigate whether the script contains exfiltration capabilities and identify the exfiltration server.
  • Assess network data to determine if the host communicated with the exfiltration server.

False positive analysis

  • Regular users do not have a business justification for using scripting utilities to capture keystrokes, making false positives unlikely. In the case of authorized benign true positives (B-TPs), exceptions can be added.

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.
  • Prioritize the response if this alert involves key executives or potentially valuable targets for espionage.
  • Restrict PowerShell usage outside of IT and engineering business units using GPOs, AppLocker, Intune, or similar software.
  • 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.
  • Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and malware components.
  • Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
  • 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).

Setup

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Setup

The PowerShell Script Block Logging logging policy must be enabled. Steps to implement the logging policy with Advanced Audit Configuration:

Computer Configuration >
Administrative Templates >
Windows PowerShell >
Turn on PowerShell Script Block Logging (Enable)

Steps to implement the logging policy via registry:

reg add "hklm\SOFTWARE\Policies\Microsoft\Windows\PowerShell\ScriptBlockLogging" /v EnableScriptBlockLogging /t REG_DWORD /d 1

Rule query

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event.category:process and host.os.type:windows and
  (
   powershell.file.script_block_text : (GetAsyncKeyState or NtUserGetAsyncKeyState or GetKeyboardState or "Get-Keystrokes") or
   powershell.file.script_block_text : (
        (SetWindowsHookA or SetWindowsHookW or SetWindowsHookEx or SetWindowsHookExA or NtUserSetWindowsHookEx) and
        (GetForegroundWindow or GetWindowTextA or GetWindowTextW or "WM_KEYBOARD_LL" or "WH_MOUSE_LL")
   )
   ) and not user.id : "S-1-5-18"
  and not powershell.file.script_block_text : (
    "sentinelbreakpoints" and "Set-PSBreakpoint"
  )

Framework: MITRE ATT&CKTM

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