4773 Security log · Kerberos Authentication Service low severity low volume

Windows Event ID 4773 — A Kerberos service ticket request failed

Kerberos TGS request failed. Failure code indicates the reason.

Why event 4773 matters

Failed TGS requests can indicate attempts to access services with invalid or expired tickets. Silver Ticket forgery attempts may generate failures.

How to detect it

Alert: high volume of TGS failures for the same ServiceName — possible Silver Ticket brute force or broken application.

Log source
Security
Advanced Audit Policy — enable the 'Kerberos Authentication Service' subcategory (Success and/or Failure).
Fields to pivot on
SubjectUserNameTargetUserNameLogonTypeIpAddressWorkstationName

Detection queries

Starting points — adapt the log source, projected fields and thresholds for your environment.

Sentinel / Defender KQL
SecurityEvent
| where EventID == 4773   // A Kerberos service ticket request failed
| project TimeGenerated, Computer, SubjectUserName, TargetUserName, LogonType, IpAddress, WorkstationName
| sort by TimeGenerated desc
Splunk SPL
index=* sourcetype="WinEventLog:Security" EventCode=4773
| stats count earliest(_time) as first_seen latest(_time) as last_seen by ComputerName
| sort - count   `# A Kerberos service ticket request failed — add EventData fields: SubjectUserName, TargetUserName, LogonType, IpAddress`
Hunt event 4773 in Sentinel/Defender →
Build a KQL query for this event in the KQL Query Builder.
Search all event IDs →
Open the interactive Windows Event ID lookup.

Related Kerberos Authentication Service events

4768 A Kerberos authentication ticket (TGT) was requested 4769 A Kerberos service ticket was requested 4770 A Kerberos service ticket was renewed 4771 Kerberos pre-authentication failed 4772 A Kerberos authentication ticket request failed 4774 An account was mapped for logon 4775 An account could not be mapped for logon 4776 The domain controller attempted to validate the credentials for an account (NTLM) 4777 The domain controller failed to validate the credentials for an account 4820 A Kerberos Ticket-Granting-Ticket (TGT) was denied because the device does not meet the access control restrictions 4821 A Kerberos service ticket was denied because the user, device, or both do not meet the access control restrictions 4822 NTLM authentication failed because the account was a member of the Protected Users group

Frequently asked questions

What is Windows Event ID 4773?

A Kerberos service ticket request failed. Kerberos TGS request failed. Failure code indicates the reason.

Which log records event 4773?

Event 4773 is written to the Security channel by Microsoft-Windows-Security-Auditing. Advanced Audit Policy — enable the 'Kerberos Authentication Service' subcategory (Success and/or Failure).

How do you detect activity around event 4773?

Alert: high volume of TGS failures for the same ServiceName — possible Silver Ticket brute force or broken application.