Event ID: 4798

Event ID 4798 is a critical security event in the Windows operating system, indicating "A user's local group membership was enumerated." This event is part of the advanced security auditing features introduced to provide deeper insight into sensitive operations that could affect the security posture of a Windows environment. It's particularly relevant in the context of monitoring and detecting potential reconnaissance activities by attackers or malicious insiders who are trying to understand the local group memberships of users, which can be a precursor to more targeted attacks.

Key Details of Event ID 4798

• Log Location: Security log.

  • %SYSTEM ROOT%\System32\winevt\logs\Security.evtx

• Category: Account Logon.

• Level: Information.

Context and Importance

The enumeration of a user's local group membership is a common step in the reconnaissance phase of an attack, where an adversary seeks to identify the local groups a user belongs to. This information can be used to tailor subsequent attacks, such as privilege escalation or lateral movement, based on the privileges associated with these groups. Therefore, monitoring Event ID 4798 can help in identifying unauthorized or suspicious enumeration activities early in the attack lifecycle.

When Event ID 4798 Is Logged

This event is logged when an application or process, such as a script run via PowerShell, queries the local group memberships of a user account. This can happen through various means, including command-line tools, scripts, or software that makes explicit calls to Windows API functions designed to retrieve group membership information.

Detailed Information Contained in the Event

An Event ID 4798 log contains several pieces of information that are crucial for analysis:

• Subject: The account that requested the enumeration. This includes the security ID (SID), account name, and domain of the user who performed the enumeration.

• Target User: The user account whose group memberships were enumerated. This includes the SID, account name, and domain.

• Caller Process ID and Name: The process ID and the name of the process that initiated the enumeration. This is critical for understanding the context of the enumeration, whether it's a legitimate system process or potentially malicious software.

• Detailed Authentication Information: Additional context about how the enumeration was performed, such as any impersonation levels.

Security Implications

Monitoring and analyzing Event ID 4798 is essential for several reasons:

• Detecting Reconnaissance Activity: Frequent or unusual patterns of group membership enumeration could indicate reconnaissance by attackers.

• Identifying Misuse of Credentials: The event can signal the misuse of legitimate credentials to gather information on group memberships, potentially for privilege escalation.

• Auditing and Compliance: For organizations subject to regulatory requirements, logging and auditing access to sensitive information, such as group memberships, can be a compliance necessity.

Analysis and Response

Security teams should incorporate the monitoring of Event ID 4798 into their security operations center (SOC) activities, using SIEM tools to aggregate and analyze these events for patterns that may indicate suspicious behavior. Correlation with other events, such as logon events (Event IDs 4624, 4625) and group modification events (Event IDs 4728, 4729), can provide a more comprehensive view of potential security incidents.

Best Practices

• Baseline Normal Activity: Understand and document normal patterns of group membership enumeration within your environment to better identify anomalies.

• Alert on Anomalies: Configure alerts for unusual patterns of enumeration, such as high frequency or enumeration performed by non-standard processes.

• Investigate and Remediate: Follow up on alerts with thorough investigations to determine the intent and scope of the enumeration, applying remediation actions as necessary to mitigate any identified threats.