Detection rules › Sigma

Findstr Launching .lnk File

Status
test
Severity
medium
Log source
product windows, category process_creation
Author
Trent Liffick
Source
github.com/SigmaHQ/sigma

Detects usage of findstr to identify and execute a lnk file as seen within the HHS redirect attack

MITRE ATT&CK coverage

Event coverage

ProviderEventTitle
SysmonEvent ID 1Process creation

Rule body yaml

title: Findstr Launching .lnk File
id: 33339be3-148b-4e16-af56-ad16ec6c7e7b
status: test
description: Detects usage of findstr to identify and execute a lnk file as seen within the HHS redirect attack
references:
    - https://www.bleepingcomputer.com/news/security/hhsgov-open-redirect-used-by-coronavirus-phishing-to-spread-malware/
author: Trent Liffick
date: 2020-05-01
modified: 2024-01-15
tags:
    - attack.stealth
    - attack.t1036
    - attack.t1202
    - attack.t1027.003
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith:
              - '\find.exe'
              - '\findstr.exe'
        - OriginalFileName:
              - 'FIND.EXE'
              - 'FINDSTR.EXE'
    selection_cli:
        CommandLine|endswith:
            - '.lnk'
            - '.lnk"'
            - ".lnk'"
    condition: all of selection_*
falsepositives:
    - Unknown
level: medium

Stages and Predicates

Stage 0: condition

all of selection_*

Stage 1: selection_img

selection_img:
    - Image|endswith:
          - '\find.exe'
          - '\findstr.exe'
    - OriginalFileName:
          - 'FIND.EXE'
          - 'FINDSTR.EXE'

Stage 2: selection_cli

selection_cli:
    CommandLine|endswith:
        - '.lnk'
        - '.lnk"'
        - ".lnk'"

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
CommandLineends_with
  • .lnk
  • .lnk"
  • .lnk'
Imageends_with
  • \find.exe corpus 8 (sigma 8)
  • \findstr.exe corpus 12 (sigma 12)
OriginalFileNameeq
  • FIND.EXE corpus 7 (sigma 7)
  • FINDSTR.EXE corpus 12 (sigma 12)