Firewall Rule Deleted Via Netsh.EXE

Status: test
Severity: medium
Log source: category process_creation, product windows
Author: frack113
Source: github.com/SigmaHQ/sigma

Detects the removal of a port or application rule in the Windows Firewall configuration using netsh

Known false positives

Legitimate administration activity
Software installations and removal

MITRE ATT&CK coverage

Tactic	Techniques
Defense Impairment	`T1686.003` Disable or Modify System Firewall: Windows Host Firewall

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation

Rule body

title: Firewall Rule Deleted Via Netsh.EXE
id: 1a5fefe6-734f-452e-a07d-fc1c35bce4b2
status: test
description: Detects the removal of a port or application rule in the Windows Firewall configuration using netsh
references:
    - https://app.any.run/tasks/8bbd5b4c-b82d-4e6d-a3ea-d454594a37cc/
author: frack113
date: 2022-08-14
modified: 2025-10-07
tags:
    - attack.defense-impairment
    - attack.t1686.003
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith: '\netsh.exe'
        - OriginalFileName: 'netsh.exe'
    selection_cli:
        CommandLine|contains|all:
            - 'firewall'
            - 'delete '
    filter_optional_dropbox:
        ParentImage|endswith: '\Dropbox.exe'
        CommandLine|contains: 'name=Dropbox'
    filter_optional_avast:
        ParentImage|endswith: '\instup.exe'
        CommandLine|contains: 'advfirewall firewall delete rule name="Avast Antivirus Admin Client"'
    condition: all of selection_* and not 1 of filter_optional_*
falsepositives:
    - Legitimate administration activity
    - Software installations and removal
level: medium

Stages and Predicates

Stage 0: `condition`

all of selection_* and not 1 of filter_optional_*

Stage 1: `selection_img`

selection_img:
    - Image|endswith: '\netsh.exe'
    - OriginalFileName: 'netsh.exe'

Stage 2: `selection_cli`

selection_cli:
    CommandLine|contains|all:
        - 'firewall'
        - 'delete '

Stage 3: `not filter_optional_*`

filter_optional_dropbox:
    ParentImage|endswith: '\Dropbox.exe'
    CommandLine|contains: 'name=Dropbox'
filter_optional_avast:
    ParentImage|endswith: '\instup.exe'
    CommandLine|contains: 'advfirewall firewall delete rule name="Avast Antivirus Admin Client"'

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`CommandLine`	match	`advfirewall firewall delete rule name="Avast Antivirus Admin Client"`	`excludes:CommandLine`
`ParentImage`	ends_with	`\instup.exe`	`excludes:ParentImage` `field:"ParentImage" value:"\instup.exe"`
`CommandLine`	match	`name=Dropbox`	`excludes:CommandLine` `field:"CommandLine" value:"name=Dropbox"`
`ParentImage`	ends_with	`\Dropbox.exe`	`excludes:ParentImage` `field:"ParentImage" value:"\Dropbox.exe"`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`delete` corpus 4 (sigma 4) `firewall` corpus 13 (sigma 7, splunk 6)	`field:"CommandLine" kind:match`
`Image`	ends_with	`\netsh.exe` corpus 28 (sigma 28)	`field:"Image" kind:ends_with value:"\netsh.exe"`
`OriginalFileName`	eq	`netsh.exe` corpus 23 (sigma 14, splunk 7, elastic 2)	`field:"OriginalFileName" kind:eq value:"netsh.exe"`

Firewall Rule Deleted Via Netsh.EXE

Known false positives

MITRE ATT&CK coverage

Telemetry coverage

Rule body

Stages and Predicates

Stage 0: condition

Stage 1: selection_img

Stage 2: selection_cli

Stage 3: not filter_optional_*

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection_img`

Stage 2: `selection_cli`

Stage 3: `not filter_optional_*`