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Windows Event ID 4771 - Kerberos pre-authentication failed

Introduction

The first time a user enters their domain username and password into their workstation, the workstation contacts a local domain controller (DC) and requests a ticket-granting ticket (TGT). If the username and password are valid and the user account passes status and restriction checks, then the DC grants a TGT and logs event ID 4768 (authentication ticket granted).

Kerberos authentication.

Windows records event ID 4771 (F) if the ticket request (Step 1 of Figure 1) failed; this event is only recorded on DCs. If the problem arose during pre-authentication (either steps 2, 3, or 4 of Figure 1), Windows records event 4768 instead.

Description of the event fields

Failed Kerberos pre-authentication event properties.

Details of a failed Kerberos pre-authentication

  • Security ID: SID of account object for which a TGT was requested.
  • Account Name: The name of the account for which a TGT was requested.

  • Service Name: The name of the service in a Kerberos realm that a TGT request was sent to.

  • Client Address: The IP address of the computer from which a TGT request was received.
  • Client Port: The source port number of a client network connection. For local host connections, the port number is 0.

  • Ticket Options: This is a set of different ticket flags displayed in hexadecimal format. The ticket flags are listed in the following table:

This information is only filled for logons with a Smart Card. It is always empty for event ID 4771.

  • Certificate Issuer Name: Name of the certification authority that issued the Smart Card certificate.
  • Certificate Serial Number: Smart Card certificate’s serial number.
  • Certificate Thumbprint: Smart Card certificate’s thumbprint.

Reasons to monitor event ID 4771

  • Monitor the Client Address field in event ID 4771 to track logon attempts that are not from your internal IP range.
  • Monitor event ID 4771 for accounts that have a Security ID that corresponds to high-value accounts, including administrators, built-in local administrators, domain administrators, and service accounts.
  • If a username is only to be used on an allowed list of IP addresses, you can monitor the Client Address field and trigger an alert whenever a logon attempt is made with a username that is not part of the white list.
  • If you have a list of accounts that are allowed to log on directly to domain controllers (rather than via network logon or Remote Desktop Connection), then you should monitor when Client Address is equal to “::1” to identify violations and possible malicious intent.
  • Monitor Subject\Account Name for names that don’t comply with your company's naming conventions.
  • Monitor this event for accounts with a Security ID that corresponds to accounts that should never be used, including non-active, disabled, and guest accounts.
  • Monitor this event to identify the use of an account outside of work hours and detect anomalies or potential malicious actions.

24/7, real-time monitoring

Although you can attach a task to the security log and ask Windows to send you an email, you are limited to simply getting an email whenever event ID 4771 is generated. Windows also lacks the ability to apply more granular filters that are required to meet security recommendations.

For example, Windows can send you an email every time event ID 4771 is generated, but it will not be able to only notify you when high-value accounts have generated the event ID, or if a Kerberos pre-authentication failure came from an unauthorized endpoint. Getting specific alerts reduces the chance of you missing out on critical notifications amongst a heap of false-positive alerts.

With a tool like ADAudit Plus, not only can you apply granular filters to focus on real threats, you can get notified in real time via SMS, too.

User and entity behavior analytics (UEBA).

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Investigate Event ID 4771 Kerberos pre-authentication failures and stop brute force attacks with ADAudit Plus.

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