SharpHound enumeration via SMB named pipes

Status: experimental
Severity: medium
Time window: 15m
Log source: product windows, service security
Author: mdecrevoisier
Source: github.com/mdecrevoisier/SIGMA-detection-rules

Detects scenarios where an attacker enumerate different host via named pipes with SharpHound for discovery purposes.

Known false positives

Administrator activity, backup solutions, Windows Server Manager

MITRE ATT&CK coverage

Tactic	Techniques
Discovery	`T1135` Network Share Discovery

Telemetry coverage

Provider	Record / event type
Security-Auditing	Event ID 5145: A network share object was checked to see whether client can be granted desired access.

Rule body

title: SharpHound enumeration via SMB named pipes
description: Detects scenarios where an attacker enumerate different host via named pipes with SharpHound for discovery purposes.
references:
- https://github.com/mdecrevoisier/EVTX-to-MITRE-Attack/tree/master/TA0007-Discovery/T1135.xxx-Network%20Share%20Discovery
- https://docs.google.com/presentation/d/1OdufXKGYPgoV1d5jDrMYSe-SYKZ7lcA4w2MFn8AkUWE/edit
- https://www.youtube.com/watch?v=_GJDkbUTSLY
- https://community.rsa.com/t5/rsa-netwitness-platform-blog/keeping-an-eye-on-your-hounds/ba-p/519889
- https://bloodhound.readthedocs.io/en/latest/data-collection/sharphound.html
tags:
- attack.discovery
- attack.t1135
author: mdecrevoisier
status: experimental
logsource:
  product: windows
  service: security
detection:
  selection:
    EventID: 5145
    ShareName: '\\*\IPC$'
    RelativeTargetName:
     - lsarpc
     - samr
     - srvsvc # May also be triggered by other tools like DonPapi, CrackMapExec
  filter:
    IpAddress: '%administration_hosts%' # List of IPs of your administration hosts to reduce false positive
  condition: selection and not filter | count(Computer) by IpAddress > 30
  timeframe: 15m
falsepositives:
- Administrator activity, backup solutions, Windows Server Manager
level: medium

Stages and Predicates

Stage 0: `condition`

selection and not filter | count(Computer) by IpAddress > 30

Stage 1: `selection`

selection:
  EventID: 5145
  ShareName: '\\*\IPC$'
  RelativeTargetName:
   - lsarpc
   - samr
   - srvsvc

Threshold: > 30

Stage 2: `not filter`

filter:
  IpAddress: '%administration_hosts%'

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`IpAddress`	eq	`%administration_hosts%`	`excludes:IpAddress` `field:"IpAddress" value:"%administration_hosts%"`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`RelativeTargetName`	eq	`lsarpc` corpus 3 (sigma 2, splunk 1) `samr` corpus 2 (sigma 2) `srvsvc` corpus 2 (sigma 2)	`field:"RelativeTargetName" kind:eq`
`ShareName`	wildcard	`\\*\IPC$` corpus 11 (sigma 11)	`field:"ShareName" kind:wildcard value:"\\*\IPC$"`