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Detection rules › Sigma

Potential Devil Bait Related Indicator

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

Detects the creation of ".xml" and ".txt" files in folders of the "\AppData\Roaming\Microsoft" directory by uncommon processes. This behavior was seen common across different Devil Bait samples and stages as described by the NCSC

MITRE ATT&CK coverage

TacticTechniques
StealthNo specific technique

Event coverage

ProviderEventTitle
SysmonEvent ID 11FileCreate

Rule body yaml

title: Potential Devil Bait Related Indicator
id: 93d5f1b4-36df-45ed-8680-f66f242b8415
status: test
description: Detects the creation of ".xml" and ".txt" files in folders of the "\AppData\Roaming\Microsoft" directory by uncommon processes. This behavior was seen common across different Devil Bait samples and stages as described by the NCSC
references:
    - https://www.ncsc.gov.uk/static-assets/documents/malware-analysis-reports/devil-bait/NCSC-MAR-Devil-Bait.pdf
author: Nasreddine Bencherchali (Nextron Systems)
date: 2023-05-15
tags:
    - detection.emerging-threats
    - attack.stealth
logsource:
    product: windows
    category: file_event
detection:
    selection:
        Image|endswith:
            - '\schtasks.exe'
            - '\wscript.exe'
            - '\mshta.exe'
        # Example folders used by the samples include:
        #   - %AppData%\Microsoft\Network\
        #   - %AppData%\Microsoft\Office\
        TargetFilename|contains: '\AppData\Roaming\Microsoft\'
        TargetFilename|endswith:
            - '.txt'
            - '.xml'
    condition: selection
falsepositives:
    - Unlikely
level: high

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    Image|endswith:
        - '\schtasks.exe'
        - '\wscript.exe'
        - '\mshta.exe'
    TargetFilename|contains: '\AppData\Roaming\Microsoft\'
    TargetFilename|endswith:
        - '.txt'
        - '.xml'

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
Imageends_with
  • \mshta.exe corpus 67 (sigma 67)
  • \schtasks.exe corpus 56 (sigma 56)
  • \wscript.exe corpus 75 (sigma 75)
TargetFilenameends_with
  • .txt corpus 3 (sigma 3)
  • .xml corpus 2 (sigma 2)
TargetFilenamematch
  • \AppData\Roaming\Microsoft\