4776 - Kerberos Authentication Attempt

https://learn.microsoft.com/en-us/windows/security/threat-protection/auditing/event-4776

Event ID 4776 is triggered in Windows environments when the Netlogon service attempts to authenticate a user or machine. This event is part of the Windows Security Log and is specifically related to the validation process of account credentials against the domain controller. It's crucial for monitoring and investigating authentication attempts, especially for identifying potential unauthorized access or troubleshooting authentication issues.

Key Details of Event ID 4776

• Log Location: Security log.

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

• Source: The source of this event is the Microsoft Authentication Package, typically noted as "MICROSOFT_AUTHENTICATION_PACKAGE_V1_0".

• Category: Audit Credential Validation

• Success: Error code will be "0x0"

When It Is Logged

Event ID 4776 is logged each time the Netlogon service is called to authenticate a user or machine, specifically when:

• A user attempts to log on at a workstation and uses a domain account.

• A service requests to authenticate a user or machine, often seen with network services or when accessing shared resources on the network.

Information Contained in the Log

An Event ID 4776 log contains several pieces of information essential for forensic analysis or troubleshooting:

• Security ID: The SID of the account that requested the authentication.

• Account Name: The name of the account that requested the authentication.

• Workstation Name: The name of the workstation from which the authentication request was made.

• Source Workstation: Similar to Workstation Name, indicating where the request originated.

• Error Code: Reflects the success or reason for failure of the authentication attempt.

  • Common error codes include

    • 0xC0000064 (user name does not exist)

    • 0xC000006A (wrong password)

    • 0xC0000234 (account locked out)

Importance of Error Code

The Error Code in event 4776 is particularly crucial for security and forensic analysis. It helps in identifying the cause of failed authentication attempts, which can indicate potential security issues such as brute force attacks, account enumeration, or credential stuffing. Understanding the error codes allows administrators to take appropriate actions, such as resetting passwords, unlocking accounts, or investigating potential security breaches.

Analyzing Event ID 4776 for Security

For security monitoring, Event ID 4776 provides valuable insights into authentication patterns and potential security threats. By analyzing these events, security teams can:

• Detect brute force attack attempts: Repeated failed logins from the same or various locations.

• Identify use of stale credentials: Failed logins due to outdated passwords.

• Monitor account lockout policies: Accounts repeatedly locked out may indicate targeted attacks or misconfigured services.

Tools and Strategies for Analysis

• Event Viewer: Directly access and filter Event ID 4776 entries for manual inspection.

• PowerShell: Automate the extraction and analysis of 4776 events from the security log.

• SIEM Systems: Aggregate and analyze 4776 events across the environment for patterns that may indicate compromised accounts or insider threats.