Detection rules › Sigma

LOLBIN Execution From Abnormal Drive

Status
test
Severity
medium
Log source
product windows, category process_creation
Author
Christopher Peacock '@securepeacock', SCYTHE '@scythe_io', Angelo Violetti - SEC Consult '@angelo_violetti', Aaron Herman
Source
github.com/SigmaHQ/sigma

Detects LOLBINs executing from an abnormal or uncommon drive such as a mounted ISO.

MITRE ATT&CK coverage

TacticTechniques
StealthNo specific technique

Event coverage

ProviderEventTitle
SysmonEvent ID 1Process creation

Rule body yaml

title: LOLBIN Execution From Abnormal Drive
id: d4ca7c59-e9e4-42d8-bf57-91a776efcb87
related:
    - id: 5b80cf53-3a46-4adc-960b-05ec19348d74
      type: similar
status: test
description: Detects LOLBINs executing from an abnormal or uncommon drive such as a mounted ISO.
references:
    - https://thedfirreport.com/2021/12/13/diavol-ransomware/
    - https://www.scythe.io/library/threat-emulation-qakbot
    - https://sec-consult.com/blog/detail/bumblebee-hunting-with-a-velociraptor/
author: Christopher Peacock '@securepeacock', SCYTHE '@scythe_io', Angelo Violetti - SEC Consult '@angelo_violetti', Aaron Herman
date: 2022-01-25
modified: 2023-08-29
tags:
    - attack.stealth
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        # Note: add more lolbins for additional coverage
        - Image|endswith:
              - '\calc.exe'
              - '\certutil.exe'
              - '\cmstp.exe'
              - '\cscript.exe'
              - '\installutil.exe'
              - '\mshta.exe'
              - '\regsvr32.exe'
              - '\rundll32.exe'
              - '\wscript.exe'
        - OriginalFileName:
              - 'CALC.EXE'
              - 'CertUtil.exe'
              - 'CMSTP.EXE'
              - 'cscript.exe'
              - 'installutil.exe'
              - 'MSHTA.EXE'
              - 'REGSVR32.EXE'
              - 'RUNDLL32.EXE'
              - 'wscript.exe'
    filter_main_currentdirectory:
        CurrentDirectory|contains: 'C:\'
    filter_main_empty:
        CurrentDirectory: ''
    filter_main_null:
        CurrentDirectory: null
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Rare false positives could occur on servers with multiple drives.
level: medium

Stages and Predicates

Stage 0: condition

selection and not 1 of filter_main_*

Stage 1: selection

selection:
    - Image|endswith:
          - '\calc.exe'
          - '\certutil.exe'
          - '\cmstp.exe'
          - '\cscript.exe'
          - '\installutil.exe'
          - '\mshta.exe'
          - '\regsvr32.exe'
          - '\rundll32.exe'
          - '\wscript.exe'
    - OriginalFileName:
          - 'CALC.EXE'
          - 'CertUtil.exe'
          - 'CMSTP.EXE'
          - 'cscript.exe'
          - 'installutil.exe'
          - 'MSHTA.EXE'
          - 'REGSVR32.EXE'
          - 'RUNDLL32.EXE'
          - 'wscript.exe'

Stage 2: not filter_main_*

filter_main_currentdirectory:
    CurrentDirectory|contains: 'C:\'
filter_main_empty:
    CurrentDirectory: ''
filter_main_null:
    CurrentDirectory: null

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

FieldKindExcluded values
CurrentDirectoryis_null(no value, null check)
CurrentDirectorymatchC:\

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
  • \calc.exe corpus 13 (sigma 13)
  • \certutil.exe corpus 43 (sigma 43)
  • \cmstp.exe corpus 8 (sigma 8)
  • \cscript.exe corpus 73 (sigma 73)
  • \installutil.exe corpus 9 (sigma 9)
  • \mshta.exe corpus 67 (sigma 67)
  • \regsvr32.exe corpus 65 (sigma 65)
  • \rundll32.exe corpus 95 (sigma 95)
  • \wscript.exe corpus 75 (sigma 75)
OriginalFileNameeq
  • CALC.EXE
  • CMSTP.EXE corpus 6 (sigma 5, elastic 1)
  • CertUtil.exe corpus 21 (sigma 14, splunk 6, elastic 1)
  • MSHTA.EXE corpus 22 (sigma 13, splunk 6, elastic 3)
  • REGSVR32.EXE corpus 26 (sigma 17, splunk 6, elastic 3)
  • RUNDLL32.EXE corpus 62 (sigma 35, splunk 21, elastic 6)
  • cscript.exe corpus 19 (sigma 17, elastic 2)
  • installutil.exe corpus 11 (sigma 6, splunk 4, elastic 1)
  • wscript.exe corpus 20 (sigma 17, elastic 3)