> For the complete documentation index, see [llms.txt](https://cortex-docs.paloaltonetworks.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://cortex-docs.paloaltonetworks.com/analytics-alerts/alerts-by-name/unusual-encrypting-file-system-remote-call-efsrpc-to-domain-controller.md).
# Unusual Encrypting File System Remote call (EFSRPC) to domain controller
### Synopsis
| Field | Value |
| -------------------- | -------------------------------------------------------------------------------------------------------- |
| Activation Period | 14 Days |
| Training Period | 30 Days |
| Test Period | N/A (single event) |
| Deduplication Period | 1 Day |
| Required Data | XDR Agent with eXtended Threat Hunting (XTH) |
| Detection Modules | Identity Analytics |
| 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 |
### Description
An unusual Encrypting File System Remote call (EFSRPC) was made to a domain controller.
### Attacker's Goals
* An attacker can abuse the Encrypting File System Remote Protocol to coerce authentication from a DC.
* This authentication can later be used for obtaining a DC certificate for DCSync.
### Investigative actions
* 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.
### Variations
A suspicious Encrypting File System Remote call (EFSRPC) was made to a domain controller
**Synopsis**
| Field | Value |
| ----------------- | -------------------------------------------------------------------------------------------------------- |
| 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 | Medium |
**Description**
An unusual Encrypting File System Remote call (EFSRPC) was made to a domain controller.
**Attacker's Goals**
* An attacker can abuse the Encrypting File System Remote Protocol to coerce authentication from a DC.
* This authentication can later be used for obtaining a DC certificate for DCSync.
**Investigative actions**
* 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.
Abnormal Encrypting File System Remote call (EFSRPC) to domain controller using EfsRpcFileKeyInfo for the first time
**Synopsis**
| Field | Value |
| ----------------- | -------------------------------------------------------------------------------------------------------- |
| 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 |
**Description**
An abnormal EfsRpcFileKeyInfo Encrypting File System Remote call (EFSRPC) was made to a domain controller for the first time.
**Attacker's Goals**
* An attacker can abuse the Encrypting File System Remote Protocol to coerce authentication from a DC.
* This authentication can later be used for obtaining a DC certificate for DCSync.
**Investigative actions**
* 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.
Abnormal Encrypting File System Remote call (EFSRPC) to domain controller using EfsRpcFileKeyInfo
**Synopsis**
| Field | Value |
| ----------------- | -------------------------------------------------------------------------------------------------------- |
| 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 | Informational |
**Description**
An abnormal EfsRpcFileKeyInfo Encrypting File System Remote call (EFSRPC) was made to a domain controller.
**Attacker's Goals**
* An attacker can abuse the Encrypting File System Remote Protocol to coerce authentication from a DC.
* This authentication can later be used for obtaining a DC certificate for DCSync.
**Investigative actions**
* 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.
---
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