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Detection rules › Sigma

Potential Commandline Obfuscation Using Escape Characters

Status
test
Severity
medium
Log source
product windows, category process_creation
Author
juju4
Source
github.com/SigmaHQ/sigma

Detects potential commandline obfuscation using known escape characters

MITRE ATT&CK coverage

TacticTechniques
StealthT1140 Deobfuscate/Decode Files or Information

Event coverage

ProviderEventTitle
SysmonEvent ID 1Process creation
Security-AuditingEvent ID 4688A new process has been created.

Rule body yaml

title: Potential Commandline Obfuscation Using Escape Characters
id: f0cdd048-82dc-4f7a-8a7a-b87a52b6d0fd
status: test
description: Detects potential commandline obfuscation using known escape characters
references:
    - https://twitter.com/vysecurity/status/885545634958385153
    - https://twitter.com/Hexacorn/status/885553465417756673 # Dead link
    - https://twitter.com/Hexacorn/status/885570278637678592 # Dead link
    - https://www.mandiant.com/resources/blog/obfuscation-wild-targeted-attackers-lead-way-evasion-techniques
    - https://web.archive.org/web/20190213114956/http://www.windowsinspired.com/understanding-the-command-line-string-and-arguments-received-by-a-windows-program/
author: juju4
date: 2018-12-11
modified: 2023-03-03
tags:
    - attack.stealth
    - attack.t1140
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        CommandLine|contains:
            # - <TAB>   # no TAB modifier in sigmac yet, so this matches <TAB> (or TAB in elasticsearch backends without DSL queries)
            - 'h^t^t^p'
            - 'h"t"t"p'
    condition: selection
falsepositives:
    - Unknown
level: medium

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    CommandLine|contains:
        - 'h^t^t^p'
        - 'h"t"t"p'

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
CommandLinematch
  • h"t"t"p
  • h^t^t^p