RPC Firewall MS-DRSR Opcode Detections from Non-Domain Controllers

title: RPC Firewall MS-DRSR Opcode Detections from Non-Domain Controllers
id: 6dde9663-c595-49fe-baf5-1feb8e4a90d8
status: test
description: This rule flags RPC Firewall events indicating access to the MS-DRSR interface (DRSR UUID) using opcode values other than 0, 1, or 12. Because MS-DRSR is used for directory replication behaviors, unexpected remote calls from non-domain controllers can indicate attempts to perform DCSync/DCShadow-style reconnaissance or replication abuse. The detection relies on RPC Firewall telemetry (EventLog RPCFW, EventID 3) including InterfaceUuid and OpNum.
references:
  - https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-drsr/f977faaa-673e-4f66-b9bf-48c640241d47?redirectedfrom=MSDN
  - https://github.com/jsecurity101/MSRPC-to-ATTACK/blob/ddd4608fe8684fcf2fcf9b48c5f0b3c28097f8a3/documents/MS-DRSR.md
  - https://github.com/zeronetworks/rpcfirewall
  - https://zeronetworks.com/blog/stopping-lateral-movement-via-the-rpc-firewall/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/application/rpc_firewall/rpc_firewall_dcsync_attack.yml
author: Sagie Dulce, Dekel Paz, Huntrule Team
date: 2022-01-01
tags:
  - attack.t1033
  - attack.discovery
logsource:
  product: rpc_firewall
  category: application
  definition: 'Requirements: install and apply the RPC Firewall to all processes, enable DRSR UUID (e3514235-4b06-11d1-ab04-00c04fc2dcd2) for "dangerous" opcodes (not 0,1 or 12) only from trusted IPs (DCs)'
detection:
  selection:
    EventLog: RPCFW
    EventID: 3
    InterfaceUuid: e3514235-4b06-11d1-ab04-00c04fc2dcd2
  filter:
    OpNum:
      - 0
      - 1
      - 12
  condition: selection and not filter
falsepositives:
  - Unknown
level: high
license: DRL-1.1
related:
  - id: 56fda488-113e-4ce9-8076-afc2457922c3
    type: derived