Event ID 4625 in the Windows Event Viewer signifies a failed attempt to log on to a local computer. This security audit event is crucial for understanding and investigating unauthorized access attempts and potential security breaches within a Windows environment.
Understanding Event ID 4625
When a user, process, or service tries to authenticate against a local machine and fails, Windows generates Event ID 4625 in the Security log. This event is always generated on the computer where the logon attempt was made, providing direct insight into the target of the failed access. It serves as a vital record for auditing and security monitoring. In contrast, Event ID 4624 records successful logon attempts, providing a complete picture of access activity.
Key Information Captured by Event ID 4625
Each Event ID 4625 entry contains specific details that help identify the nature of the failed logon attempt. Analyzing these fields is essential for proper investigation.
| Field Name | Description |
|---|---|
| Account Name | The user account name that attempted to log on. This can be a legitimate user, a service account, or an unknown account. |
| Source Network Address | The IP address or hostname from which the logon attempt originated. Crucial for identifying the source of malicious activity. |
| Logon Type | Indicates the type of logon attempt (e.g., network, interactive, remote interactive). |
| Failure Reason | A detailed explanation for why the logon failed. This is often represented by a "SubStatus" or "Status" code. |
| Process Information | Details about the process that initiated the logon attempt, useful for identifying applications or services causing issues. |
Why Monitoring Event ID 4625 is Crucial
Monitoring failed logon attempts is a cornerstone of robust cybersecurity. These events provide early warnings for various security issues:
- Brute-Force Attacks: A high volume of 4625 events from a single source against multiple accounts, or against one account, often indicates a brute-force attack where an attacker is trying to guess passwords.
- Account Lockouts: Repeated failed logons can trigger account lockout policies, disrupting legitimate user access. Monitoring helps diagnose and resolve these issues promptly.
- Credential Stuffing: Attackers often use leaked credentials from other breaches to try and log into accounts on different services. Event ID 4625 can flag these attempts.
- Misconfigurations or User Errors: Sometimes, failed logons are due to simple mistakes like incorrect passwords, expired credentials, or misconfigured applications or services trying to authenticate with outdated information.
- Insider Threats: Monitoring can also reveal suspicious activity from internal sources, indicating potential insider threats or unauthorized access attempts by employees.
Common Reasons for Failed Logons
The "Failure Reason" or "SubStatus" code within Event ID 4625 provides specific context for why the logon failed. Here are some common reasons:
- 0xC000006A: User name or password is incorrect. This is one of the most common reasons and often points to user error or brute-force attempts.
- 0xC0000234: The user account is currently locked out and may not be logged on to. This occurs after too many failed password attempts.
- 0xC000006F: The user has not been granted the requested logon type at this machine. This could indicate a policy restriction.
- 0xC0000072: The specified account has expired.
- 0xC000006E: The specified account name is not recognized or is invalid. This might indicate an attempt to log on with a non-existent username.
- 0xC0000070: The user account has time restrictions and cannot be logged on to at this time.
- 0xC0000193: The user account's password has expired.
Understanding these codes helps quickly diagnose the problem. For a comprehensive list of specific failure codes, administrators often refer to detailed Microsoft security auditing documentation.
What to Do When You See Event ID 4625
Responding effectively to Event ID 4625 is critical for maintaining system security:
- Investigate the Source: Determine the source IP address or hostname. Is it internal or external? Is it a known device?
- Analyze the Account: Identify the target account. Is it a privileged account (e.g., Administrator)? Is it a commonly used account?
- Check Frequency and Patterns: A single failure might be a typo. Numerous failures from one source against one or many accounts suggest malicious activity. Look for patterns in time, frequency, and targeted accounts.
- Review Failure Reason (SubStatus): Use the SubStatus code to understand why the logon failed. This guides troubleshooting or investigation.
- Take Action:
- User Error: Inform the user, reset password if necessary.
- Account Lockout: Unlock the account, investigate the cause of lockouts (e.g., misconfigured service, repeated bad passwords).
- Suspected Attack: Block the source IP address, reset the target account's password, enable multi-factor authentication, and review other security logs (e.g., firewall logs).
- Misconfiguration: Correct application credentials or service account settings.
- Implement Automated Monitoring: Use Security Information and Event Management (SIEM) systems or dedicated monitoring tools to automatically alert on suspicious Event ID 4625 patterns, enhancing proactive threat detection.
By diligently monitoring and understanding Event ID 4625, organizations can significantly enhance their ability to detect, prevent, and respond to unauthorized access attempts and maintain a secure computing environment.
