Windows Network Access Suspicious desktop.ini Action

Status: test
Severity: medium
Log source: product windows, service security
Author: Tim Shelton (HAWK.IO)
Source: github.com/SigmaHQ/sigma

Detects unusual processes accessing desktop.ini remotely over network share, which can be leveraged to alter how Explorer displays a folder's content (i.e. renaming files) without changing them on disk.

Known false positives

Read only access list authority

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	`T1547.009` Boot or Logon Autostart Execution: Shortcut Modification
Privilege Escalation	`T1547.009` Boot or Logon Autostart Execution: Shortcut Modification

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: Windows Network Access Suspicious desktop.ini Action
id: 35bc7e28-ee6b-492f-ab04-da58fcf6402e
status: test
description: Detects unusual processes accessing desktop.ini remotely over network share, which can be leveraged to alter how Explorer displays a folder's content (i.e. renaming files) without changing them on disk.
references:
    - https://isc.sans.edu/forums/diary/Desktopini+as+a+postexploitation+tool/25912/
author: Tim Shelton (HAWK.IO)
date: 2021-12-06
modified: 2022-01-16
tags:
    - attack.privilege-escalation
    - attack.persistence
    - attack.t1547.009
logsource:
    product: windows
    service: security
detection:
    selection:
        EventID: 5145
        ObjectType: File
        RelativeTargetName|endswith: '\desktop.ini'
        AccessList|contains:
            - 'WriteData'
            - 'DELETE'
            - 'WriteDAC'
            - 'AppendData'
            - 'AddSubdirectory'
    condition: selection
falsepositives:
    - Read only access list authority
level: medium

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    EventID: 5145
    ObjectType: File
    RelativeTargetName|endswith: '\desktop.ini'
    AccessList|contains:
        - 'WriteData'
        - 'DELETE'
        - 'WriteDAC'
        - 'AppendData'
        - 'AddSubdirectory'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`AccessList`	match	`AddSubdirectory` `AppendData` `DELETE` `WriteDAC` `WriteData` corpus 4 (sigma 4)	`field:"AccessList" kind:match`
`ObjectType`	eq	`File` corpus 10 (sigma 8, splunk 2)	`field:"ObjectType" kind:eq value:"File"`
`RelativeTargetName`	ends_with	`\desktop.ini`	`field:"RelativeTargetName" kind:ends_with value:"\desktop.ini"`