Enable PowerShell Script Block Logging (Detective, not preventative)

What is Enabling PowerShell Script Block Logging?

PowerShell Script Block Logging is a security feature that records detailed information about the execution of PowerShell scripts, including the contents of the scripts themselves. This logging can capture both the commands and the script blocks (chunks of code) that are executed, providing deep visibility into PowerShell activities, which is essential for security monitoring and forensic analysis.

What is Enabling PowerShell Script Block Logging?

Enabling PowerShell Script Block Logging involves configuring the system to log all script blocks processed by the PowerShell engine. This includes both commands entered in the PowerShell console and scripts executed on the system. The logs are stored in the Windows Event Log, under the Microsoft-Windows-PowerShell/Operational log.

Risks of PowerShell Script Block Logging being Disabled:

If Script Block Logging is disabled, the following risks may be present:

  1. Limited Visibility: Without script block logging, security teams may miss key indicators of compromise (IOCs) within PowerShell activity, making it harder to detect and respond to attacks that use PowerShell.

  2. Undetected Malicious Activity: Attackers can execute malicious scripts or commands without leaving sufficient evidence, allowing them to go undetected for longer periods.

  3. Forensic Gaps: In the event of a security breach, the absence of detailed script execution logs can hinder forensic investigations and delay incident response efforts.

Why this Remediation Effort is Important:

Enabling PowerShell Script Block Logging is crucial for enhancing security monitoring and forensic capabilities within the client’s environment. With the rise of PowerShell-based attacks, having detailed logs of all executed script blocks provides valuable insights into potential malicious activities. This logging also aids in compliance with security frameworks and regulatory requirements that mandate thorough monitoring of script executions.

Potential Implementation Impacts to Watch Out For:

  1. Increased Log Volume: Script Block Logging generates a significant amount of data, which could increase the size of event logs and place additional storage demands on log management systems.

  2. Performance Considerations: While the performance impact of enabling Script Block Logging is generally minimal, in environments with heavy PowerShell usage, there could be a slight performance degradation.

  3. Sensitive Data Exposure: Logging all script content may inadvertently capture and store sensitive information in the logs. It’s important to ensure proper log management and protection practices are in place.

Technical Deployment: Creating a GPO for Enabling PowerShell Script Block Logging:

  1. Open Group Policy Management Console (GPMC):

    • Go to Start > Administrative Tools > Group Policy Management.

  2. Create or Edit a GPO:

    • Right-click the desired Organizational Unit (OU) or domain, and select Create a GPO in this domain, and link it here.

    • Name the GPO something descriptive, like “Enable PowerShell Script Block Logging”.

  3. Configure the GPO:

    • Navigate to Computer Configuration > Administrative Templates > Windows Components > Windows PowerShell.

    • Locate the setting Turn on PowerShell Script Block Logging and set it to Enabled.

    • Ensure the setting Turn on Module Logging is also configured if additional logging of module activities is required.

    • Apply the GPO.

  4. Deploy the GPO:

    • Once configured, deploy the GPO to the desired OUs or across the domain.

Implementation Tip:

  1. Monitoring: After enabling Script Block Logging, configure your Security Information and Event Management (SIEM) system or centralized logging solution to collect and analyze the logs from the Microsoft-Windows-PowerShell/Operational event log. This will help in promptly identifying suspicious activities.

  2. Log Retention: Review and adjust the log retention policies to ensure that the increased volume of logs does not overwhelm your log storage systems.

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