What is Event ID 4776: Domain Controller Attempted to Validate the Credentials for an Account. Many security events with odd usernames, misspelled names, attempts with expired or locked out accounts, or unusual logon attempts outside of business hours may be recorded by our domain controller’s Windows Event Viewer and given the Event ID 4776. Understanding how to troubleshoot and monitor these events help to spot potential brute-force attacks or malicious account usage.
Let’s start the article What is Event ID 4776: Domain Controller Attempted to Validate the Credentials for an Account.
The event ID 4776 appeared while we reviewed the event logs on a Domain Controller (DC). We learn from this event that a particular DC (servers and workstations) was used as a logon server to verify credentials. For instance, when the DC tries to verify an account’s credentials using NTLM (NT LAN Manager), Windows logs this event ID, which we discuss in the following section.
Overview of Windows Event ID 4776
The domain controller records every attempt to log in on the DC. When the DC verifies the credentials and either successfully or unsuccessfully attempts to authenticate a user using NTLM (not Kerberos), it logs this event ID. Additionally, if a workstation or server validates credentials using a local SAM account during a logon attempt, the 4776 type is recorded on the local machine.
Windows Event ID 4776 Error Code Details
- If the Error Code field is equal to 0x0, it indicates that Windows has successfully validated the credentials, resulting in an “Authentication Success – Event ID 4776 (S)” event without errors.
- Windows did not correctly validate the credentials, resulting in an “Authentication Failure – Event ID 4776 (F)” event if the Error Code field is not equal to 0x0. The Error Code is not 0x0 in this situation. When it is not equal to 0x0, refer to the table below for a description of the error code.
Troubleshooting Windows Event ID 4776
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Solving Windows Event ID 4776 Failed Attempts
When securing a Windows-based network, one crucial aspect is monitoring and responding to failed login attempts. In particular, Windows Event records such events, which signals security breaches or misconfigurations. To address these issues, IT professionals must identify each failed attempt’s source and nature. In this section, we explore various techniques and tools for solving Windows Event’s failed attempts, including determining the source workstation and account, using packet sniffers and network debuggers, and securing remote connections.
Determining the Source
The account name and the originating workstation are displayed the ID 4776, as we discovered in the previous section. Remember that NTLM authentication allows us to identify the user or machine rapidly. However, the source workstation might try to log in from outside with a blank name and a random (made-up) account. It would help, if we looked further.
Leverage the Other Tools
- Packet Sniffer: Use third-party software installed on the DC, such as Wireshark, to record the traffic occurring concurrently with these occurrences. To pinpoint the particular source of these events, use Wireshark’s capture and display filters. Additionally, we match the precise moment this event occurs in Wireshark and Windows Event Viewer. Additionally, we quickly locate IP addresses with Wireshark to begin constructing a more accurate picture of the origin of these logins.
- Network Debugger: A network debugger is yet another valuable outside resource. On our DC, enable the NetLogon debugging tool. Windows records the authentication requests in a log file created by this tool. We look over this log file to determine where they originated.
- DCDiag: A Domain Controller Health Check tool called DCDiag aids in troubleshooting. The DCdiag performs various health checks on the DC and logs extra information such as problems, warnings, or informational messages. To increase the output size, run the DCDiag using the verbose output option (/v).
Check for Open Port
The system administrator may have opened port 3389, remote desktop protocol (RDP), for users who connect remotely to computers inside the domain, if a remote client attempts to log in using that protocol. Remember when using RDP that it prefers Kerberos for authentication but falls back to NTLM, if it fails. Because of this, we might have gotten Event ID from a workstation with an unknown source. We might try the following solutions:
Importance of Monitoring Windows Event ID 4776
Keep an eye on Windows 4776 to keep track of every NTLM authentication attempt made in our domain. Look for events, that Windows started when unauthorized accounts were involved or when NTLM wasn’t necessary in the first place. Considering that we only use NTLM for local logon attempts, we should use a VPN rather than RDP.
Reasons to Monitor Event ID 4776:
- Identify the relay and cracking attacks: Perpetrators use relay attacks (false information interception) against the NTLM authentication method. First and foremost, NTLM is incompatible with contemporary encryption methods like SHA-256 and AES-256. It is also susceptible to offline cracking attacks because it lacks encryption.
- Find brute force or enumeration attacks: Keep track of multiple login attempts that occur quickly and with specific characteristics, such as using various wrong usernames, by monitoring Windows Event ID 4776. This behavior is closely related to enumeration and reverse brute force attacks. Similarly, we observe this event and search for numerous logon attempts over short intervals with wrong (or misspelled) passwords. Attacks using brute force are related to this phenomenon.
- Find potential malicious intent: We identify logon attempts made outside regular business hours or from unauthorized workstations by keeping track of the Windows Event ID 4776. These logon attempts could indicate nefarious intent, if they originate from high-value accounts. Attempts to log in using accounts that are locked, expired, or disabled could indicate misuse of resources.
Although it may be best to avoid these NTLM vulnerabilities and use more secure protocols like Kerberos (v5), doing so will ultimately reduce productivity and usability. Numerous NTLM authentication requests still require verification.
The primary authentication technique in Active Directory environments is currently Kerberos. But as a best practice, it is advised to audit all security logs and events associated with NTLM authentication before switching to more secure protocols like Kerberos and forcing Windows to restrict NTLM traffic.
Monitoring the Windows Event ID 4776
We should regularly check certain event logs, such as the Windows Event ID 4776.
By connecting a job to a particular event or log, Windows Event Viewer (available in Windows Vista 7, Server 2008, and subsequent versions) enables automation. Link an event that Windows generates, such as Event ID 4776, to a specific automated activity. For example, saying, “Send me an email when Windows Event ID 4776 is generated,” is one way to link it to an email.
There are several restrictions with Windows Event Viewer, particularly concerning its alerting and reporting engine. For example, the email won’t provide specific details about the mistakes, such as their nature (such as attempts from unapproved workstations, restricted accounts, misspelled usernames, or errors that occurred outside of regular business hours). Furthermore, Event Viewer does not offer granular filtering options to aid in finding what we are looking for.
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What is Event ID 4776: Domain Controller Attempted to Validate the Credentials for an Account Conclusion
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