Unusual Encrypting File System Remote call (EFSRPC) to domain controller

Cortex XSIAM Analytics Alert Reference by Alert name

Product

Cortex XSIAM

Last date published

2025-01-19

Activation Period	14 Days
Training Period	30 Days
Test Period	N/A (single event)
Deduplication Period	1 Day
Required Data	Requires: XDR Agent with eXtended Threat Hunting (XTH)
Detection Modules
Detector Tags
ATT&CK Tactic	Credential Access (TA0006)
ATT&CK Technique	Forced Authentication (T1187) Adversary-in-the-Middle: LLMNR/NBT-NS Poisoning and SMB Relay (T1557.001)
Severity	Low

An unusual Encrypting File System Remote call (EFSRPC) was made to a domain controller.

An attacker can abuse the Encrypting File System Remote Protocol to coerce an authentication from a DC.
This authentication can later be used for obtaining a DC certificate for DCSync.

Check for a suspicious process on the initiator.
Check if the source host is a vulnerability scanner.
Check for unusual connections from the server of the requested file location (it may be a relay server).
Look for unusual AD CS certificate requests.
Look for following suspicious connections using the DC machine account.
Check for possible DCSync alerts.

ATT&CK Tactic

ATT&CK Technique

Severity

Medium

An unusual Encrypting File System Remote call (EFSRPC) was made to a domain controller.

An attacker can abuse the Encrypting File System Remote Protocol to coerce an authentication from a DC.
This authentication can later be used for obtaining a DC certificate for DCSync.

Check for a suspicious process on the initiator.
Check if the source host is a vulnerability scanner.
Check for unusual connections from the server of the requested file location (it may be a relay server).
Look for unusual AD CS certificate requests.
Look for following suspicious connections using the DC machine account.
Check for possible DCSync alerts.