4928 Security log · DS Access info severity low volume

Windows Event ID 4928 — An Active Directory replica source naming context was established

A DC established a replication naming context. Part of normal AD replication.

Why event 4928 matters

DCSync and replication attacks may generate these. Monitor for non-DC sources establishing replication contexts.

How to detect it

Alert: non-DC computer accounts appearing as replication sources. Normal: DC computer accounts (ending in $).

Log source
Security
Advanced Audit Policy — enable the 'DS Access' 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 == 4928   // An Active Directory replica source naming context was established
| project TimeGenerated, Computer, SubjectUserName, TargetUserName, LogonType, IpAddress, WorkstationName
| sort by TimeGenerated desc
Splunk SPL
index=* sourcetype="WinEventLog:Security" EventCode=4928
| stats count earliest(_time) as first_seen latest(_time) as last_seen by ComputerName
| sort - count   `# An Active Directory replica source naming context was established — add EventData fields: SubjectUserName, TargetUserName, LogonType, IpAddress`
Hunt event 4928 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 DS Access events

4662 An operation was performed on an object 4929 An Active Directory replica source naming context was removed 4930 An Active Directory replica source naming context was modified 4932 Synchronization of a replica of an Active Directory naming context has begun 4933 Synchronization of a replica of an Active Directory naming context has ended 4934 Attributes of an Active Directory object were replicated 4935 Replication failure begins 4936 Replication failure ends 4937 A lingering object was removed from the replica 5136 A directory service object was modified 5137 A directory service object was created 5138 A directory service object was undeleted

Frequently asked questions

What is Windows Event ID 4928?

An Active Directory replica source naming context was established. A DC established a replication naming context. Part of normal AD replication.

Which log records event 4928?

Event 4928 is written to the Security channel by Microsoft-Windows-Security-Auditing. Advanced Audit Policy — enable the 'DS Access' subcategory (Success and/or Failure).

How do you detect activity around event 4928?

Alert: non-DC computer accounts appearing as replication sources. Normal: DC computer accounts (ending in $).