Detection rules › Sigma

Network Connection Initiated From Users\Public Folder

Status
test
Severity
medium
Log source
category network_connection, product windows
Author
Florian Roth (Nextron Systems)
Source
github.com/SigmaHQ/sigma

Detects a network connection initiated from a process located in the "C:\Users\Public" folder. Attacker are known to drop their malicious payloads and malware in this directory as its writable by everyone. Use this rule to hunt for potential suspicious or uncommon activity in your environement.

Known false positives

  • Likely from legitimate third party application that execute from the "Public" directory.

MITRE ATT&CK coverage

TacticTechniques
Command & Control

Telemetry coverage

ProviderRecord / event type
SysmonEvent ID 3: Network connection

Rule body

title: Network Connection Initiated From Users\Public Folder
id: bcb03938-9f8b-487d-8d86-e480691e1d71
related:
    - id: 7b434893-c57d-4f41-908d-6a17bf1ae98f
      type: derived
status: test
description: |
    Detects a network connection initiated from a process located in the "C:\Users\Public" folder.
    Attacker are known to drop their malicious payloads and malware in this directory as its writable by everyone.
    Use this rule to hunt for potential suspicious or uncommon activity in your environement.
references:
    - https://docs.google.com/spreadsheets/d/17pSTDNpa0sf6pHeRhusvWG6rThciE8CsXTSlDUAZDyo
author: Florian Roth (Nextron Systems)
date: 2024-05-31
tags:
    - attack.command-and-control
    - attack.t1105
    - detection.threat-hunting
logsource:
    category: network_connection
    product: windows
detection:
    selection:
        Initiated: 'true'
        Image|contains: ':\Users\Public\'
    filter_optional_ibm:
        Image|contains: ':\Users\Public\IBM\ClientSolutions\Start_Programs\' # IBM Client Solutions Default Location (Added by Tim Shelton - https://github.com/SigmaHQ/sigma/pull/3053/files)
    condition: selection and not 1 of filter_optional_*
falsepositives:
    - Likely from legitimate third party application that execute from the "Public" directory.
level: medium

Stages and Predicates

Stage 0: condition

selection and not 1 of filter_optional_*

Stage 1: selection

selection:
    Initiated: 'true'
    Image|contains: ':\Users\Public\'

Stage 2: not filter_optional_ibm

filter_optional_ibm:
    Image|contains: ':\Users\Public\IBM\ClientSolutions\Start_Programs\'

Exclusions

The rule actively suppresses these predicates.

FieldKindExcluded valuesSearch
Imagematch:\Users\Public\IBM\ClientSolutions\Start_Programs\excludes:Image field:"Image" value:":\Users\Public\IBM\ClientSolutions\Start_Programs\"

Indicators

These rows show field, operator, and value matches.

FieldKindValuesSearch
Imagematch
  • :\Users\Public\ corpus 13 (sigma 13)
field:"Image" kind:match value:":\Users\Public\"
Initiatedeq
  • true corpus 50 (sigma 50)
field:"Initiated" kind:eq value:"true"