Renamed Gpg.EXE Execution

Status: test
Severity: high
Log source: category process_creation, product windows
Author: Nasreddine Bencherchali (Nextron Systems), frack113
Source: github.com/SigmaHQ/sigma

Detects the execution of a renamed "gpg.exe". Often used by ransomware and loaders to decrypt/encrypt data.

MITRE ATT&CK coverage

Tactic	Techniques
Impact	`T1486` Data Encrypted for Impact

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation

Rule body

title: Renamed Gpg.EXE Execution
id: ec0722a3-eb5c-4a56-8ab2-bf6f20708592
status: test
description: Detects the execution of a renamed "gpg.exe". Often used by ransomware and loaders to decrypt/encrypt data.
references:
    - https://securelist.com/locked-out/68960/
author: Nasreddine Bencherchali (Nextron Systems), frack113
date: 2023-08-09
tags:
    - attack.impact
    - attack.t1486
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        OriginalFileName: 'gpg.exe'
    filter_main_img:
        Image|endswith:
            - '\gpg.exe'
            - '\gpg2.exe'
    condition: selection and not 1 of filter_main_*
level: high

Stages and Predicates

Stage 0: `condition`

selection and not 1 of filter_main_*

Stage 1: `selection`

selection:
    OriginalFileName: 'gpg.exe'

Stage 2: `not filter_main_img`

filter_main_img:
    Image|endswith:
        - '\gpg.exe'
        - '\gpg2.exe'

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`Image`	ends_with	`\gpg.exe`	`excludes:Image` `field:"Image" value:"\gpg.exe"`
`Image`	ends_with	`\gpg2.exe`	`excludes:Image` `field:"Image" value:"\gpg2.exe"`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`OriginalFileName`	eq	`gpg.exe` corpus 2 (sigma 2)	`field:"OriginalFileName" kind:eq value:"gpg.exe"`