Base64 MZ Header In CommandLine

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

Detects encoded base64 MZ header in the commandline

Known false positives

Unlikely

MITRE ATT&CK coverage

Tactic	Techniques
Execution	No specific technique

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation
Security-Auditing	Event ID 4688: A new process has been created.

Rule body

title: Base64 MZ Header In CommandLine
id: 22e58743-4ac8-4a9f-bf19-00a0428d8c5f
status: test
description: Detects encoded base64 MZ header in the commandline
references:
    - https://thedfirreport.com/2022/07/11/select-xmrig-from-sqlserver/
author: Nasreddine Bencherchali (Nextron Systems)
date: 2022-07-12
tags:
    - attack.execution
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        CommandLine|contains:
            - 'TVqQAAMAAAAEAAAA' # MZ..........
            - 'TVpQAAIAAAAEAA8A'
            - 'TVqAAAEAAAAEABAA'
            - 'TVoAAAAAAAAAAAAA'
            - 'TVpTAQEAAAAEAAAA'
    condition: selection
falsepositives:
    - Unlikely
level: high

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    CommandLine|contains:
        - 'TVqQAAMAAAAEAAAA'
        - 'TVpQAAIAAAAEAA8A'
        - 'TVqAAAEAAAAEABAA'
        - 'TVoAAAAAAAAAAAAA'
        - 'TVpTAQEAAAAEAAAA'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`TVoAAAAAAAAAAAAA` `TVpQAAIAAAAEAA8A` `TVpTAQEAAAAEAAAA` `TVqAAAEAAAAEABAA` `TVqQAAMAAAAEAAAA`	`field:"CommandLine" kind:match`

Base64 MZ Header In CommandLine

Known false positives

MITRE ATT&CK coverage

Telemetry coverage

Rule body

Stages and Predicates

Stage 0: condition

Stage 1: selection

Indicators

Stage 0: `condition`

Stage 1: `selection`