RPC Firewall: SASec scheduled task reconnaissance (OpNum 0/1) via MS-TSCH

title: "RPC Firewall: SASec scheduled task reconnaissance (OpNum 0/1) via MS-TSCH"
id: 6193be6b-e775-4fef-b938-b24695d6b2e3
status: test
description: This rule flags RPC Firewall EventLog entries (RPCFW) indicating remote RPC access to the SASec interface used for scheduled tasks discovery. Attackers may use these calls to enumerate task-related information as part of reconnaissance. It relies on RPC Firewall telemetry, specifically EventID 3 with the SASec interface UUID and captures the matching operation numbers except the excluded OpNum values.
references:
  - https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-tsch/d1058a28-7e02-4948-8b8d-4a347fa64931
  - https://github.com/jsecurity101/MSRPC-to-ATTACK/blob/ddd4608fe8684fcf2fcf9b48c5f0b3c28097f8a3/documents/MS-TSCH.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_sasec_recon.yml
author: Sagie Dulce, Dekel Paz, Huntrule Team
date: 2022-01-01
tags:
  - attack.discovery
logsource:
  product: rpc_firewall
  category: application
  definition: 'Requirements: install and apply the RPC Firewall to all processes with "audit:true action:block uuid:378e52b0-c0a9-11cf-822d-00aa0051e40f"'
detection:
  selection:
    EventLog: RPCFW
    EventID: 3
    InterfaceUuid: 378e52b0-c0a9-11cf-822d-00aa0051e40f
  filter:
    OpNum:
      - 0
      - 1
  condition: selection and not filter
falsepositives:
  - Unknown
level: high
license: DRL-1.1
related:
  - id: 0a3ff354-93fc-4273-8a03-1078782de5b7
    type: derived