Detection rules › Sigma

OpenSSH server firewall configuration on Windows (firewall)

Status
experimental
Severity
high
Log source
product windows, service firewall-as
Author
mdecrevoisier
Source
github.com/mdecrevoisier/SIGMA-detection-rules

Detects scenarios where an attacker configure the Windows firewall to allow incoming connections to perform stealthy lateral movement.

MITRE ATT&CK coverage

Event coverage

Rule body yaml

title: OpenSSH server firewall configuration on Windows (firewall)
description: Detects scenarios where an attacker configure the Windows firewall to allow incoming connections to perform stealthy lateral movement.
references:
 - https://github.com/mdecrevoisier/EVTX-to-MITRE-Attack/tree/master/TA0008-Lateral%20Movement/T1021.004-Remote%20Service%20SSH
 - https://winaero.com/enable-openssh-server-windows-10/
 - https://docs.microsoft.com/en-us/windows-server/administration/openssh/openssh_install_firstuse
 - https://virtualizationreview.com/articles/2020/05/21/ssh-server-on-windows-10.aspx
 - https://www.microsoft.com/en-us/security/blog/2022/10/18/defenders-beware-a-case-for-post-ransomware-investigations/
tags:
- attack.defense_evasion
- attack.t1562.004
author: mdecrevoisier
status: experimental
logsource:
  product: windows
  service: firewall-as
detection:
  selection_event:
    EventID: 2004

  selection_process: # New firewall rule creation (process focus)
    ApplicationPath|endswith: '\sshd.exe' # full path 'C:\Windows\system32\OpenSSH\sshd.exe'

  selection_port:  # New firewall rule creation (port focus)
    LocalPorts: 22 # Attackers may change port 

  condition: selection_event and (selection_process or selection_port)
falsepositives:
- Unknown
level: high

Stages and Predicates

Stage 0: condition

selection_event and (selection_process or selection_port)

Stage 1: selection_event

selection_event:
  EventID: 2004

Stage 2: selection_process

selection_process:
  ApplicationPath|endswith: '\sshd.exe'

Stage 3: selection_port

selection_port:
  LocalPorts: 22

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
ApplicationPathends_with
  • \sshd.exe
LocalPortseq
  • 22