Kerberos pre-authentication failed

// EVENT DEFINITION:

Kerberos pre-authentication verification failed (`bad password or AS-REP Roasting attempt`).

// DETAILED TELEMETRY & CONTEXT:

Event ID 4771 is generated on Domain Controllers when a user enters an incorrect password during initial pre-authentication (`Failure Code: 0x18`). If an account has `Do not require Kerberos preauthentication` (`UF_DONT_REQUIRE_PREAUTH`) enabled, attackers request TGT hashes directly without a password—known as **AS-REP Roasting**.

[ ! ]Failure Reason / Root Cause Analysis

User mistyping domain password, brute-force attacks, or AS-REP Roasting attempts against vulnerable accounts.

Operational Metadata & Applicability

Log Category:Kerberos

Audit Type Classification:Failure Audit

Supported Operating Systems:Windows Server 2016, 2019, 2022 / Windows Client 10, 11 (Enterprise / Pro)

Threat Hunting Keywords:

pre-authentication failedas-rep roasting0x18kerberos errorpreauth

MITRE ATT&CK Framework Alignment

T1558.004

Steal or Forge Kerberos Tickets: AS-REP RoastingTactic: Credential Access

T1110

Brute ForceTactic: Credential Access

Mitigation Playbook & Recommended SOC Actions

•Audit Active Directory to identify and disable `Do not require Kerberos preauthentication` on all user accounts (`prevent AS-REP Roasting`).
•Correlate spikes in Event 4771 (`Failure Code: 0x18`) with Event 4625 across external gateway IP ranges.

Representative Windows Event XML Schema

<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="Microsoft-Windows-Security-Auditing" Guid="{54849625-5478-4994-A5BA-3E3B0328C30D}" />
    <EventID>4771</EventID>
    <Version>0</Version>
    <Level>0</Level>
    <Task>12544</Task>
    <Opcode>0</Opcode>
    <Keywords>0x8020000000000000</Keywords>
    <TimeCreated SystemTime="2026-07-17T09:54:44.327Z" />
    <EventRecordID>1048576</EventRecordID>
    <Correlation />
    <Execution ProcessID="612" ThreadID="1024" />
    <Channel>Security</Channel>
    <Computer>DC01.enterprise.internal</Computer>
    <Security />
  </System>
  <EventData>
    <Data Name="SubjectUserSid">S-1-5-18</Data>
    <Data Name="SubjectUserName">SYSTEM</Data>
    <Data Name="SubjectDomainName">NT AUTHORITY</Data>
    <Data Name="SubjectLogonId">0x3e7</Data>
    <!-- Event telemetry fields specific to Kerberos pre-authentication failed -->
  </EventData>
</Event>

Correlated / Related Security Event IDs

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