Potential COLDSTEEL RAT File Indicators

Status: test
Severity: high
Log source: category file_event, product windows
Author: Nasreddine Bencherchali (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects the creation of a file named "dllhost.exe" in the "C:\users\public\Documents" directory. Seen being used by the COLDSTEEL RAT in some of its variants.

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	No specific technique
Stealth	No specific technique

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 11: FileCreate

Rule body

title: Potential COLDSTEEL RAT File Indicators
id: c708a93f-46b4-4674-a5b8-54aa6219c5fa
status: test
description: Detects the creation of a file named "dllhost.exe" in the "C:\users\public\Documents\" directory. Seen being used by the COLDSTEEL RAT in some of its variants.
references:
    - https://www.ncsc.gov.uk/static-assets/documents/malware-analysis-reports/cold-steel/NCSC-MAR-Cold-Steel.pdf
author: Nasreddine Bencherchali (Nextron Systems)
date: 2023-04-30
tags:
    - attack.persistence
    - detection.emerging-threats
    - attack.stealth
logsource:
    category: file_event
    product: windows
detection:
    selection:
        TargetFilename: 'C:\users\public\Documents\dllhost.exe'
    condition: selection
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    TargetFilename: 'C:\users\public\Documents\dllhost.exe'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`TargetFilename`	eq	`C:\users\public\Documents\dllhost.exe`	`field:"TargetFilename" kind:eq value:"C:\users\public\Documents\dllhost.exe"`