Qakbot Regsvr32 Calc Pattern

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

Detects a specific command line of "regsvr32" where the "calc" keyword is used in conjunction with the "/s" flag. This behavior is often seen used by Qakbot

Known false positives

Unlikely

MITRE ATT&CK coverage

Tactic	Techniques
Execution	No specific technique
Stealth	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: Qakbot Regsvr32 Calc Pattern
id: 0033cf83-fb87-446d-9cac-43d63ad4d5a9
status: test
description: Detects a specific command line of "regsvr32" where the "calc" keyword is used in conjunction with the "/s" flag. This behavior is often seen used by Qakbot
references:
    - https://github.com/pr0xylife/Qakbot/
author: Nasreddine Bencherchali (Nextron Systems)
date: 2023-05-26
modified: 2024-03-05
tags:
    - attack.execution
    - detection.emerging-threats
    - attack.stealth
logsource:
    product: windows
    category: process_creation
detection:
    selection:
        Image|endswith: '\regsvr32.exe'
        CommandLine|contains|windash: ' -s'
        CommandLine|endswith: ' calc'
    condition: selection
falsepositives:
    - Unlikely
level: high

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    Image|endswith: '\regsvr32.exe'
    CommandLine|contains|windash: ' -s'
    CommandLine|endswith: ' calc'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	ends_with	`calc`	`field:"CommandLine" kind:ends_with value:" calc"`
`CommandLine`	match	`-s` transforms: `windash` corpus 3 (sigma 3)	`field:"CommandLine" kind:match value:" -s"`
`Image`	ends_with	`\regsvr32.exe` corpus 64 (sigma 64)	`field:"Image" kind:ends_with value:"\regsvr32.exe"`