Detection rules › Sigma

macOS ULS securityd CodeSignature Failure

Status
experimental
Severity
medium
Log source
product macos, service unifiedlog
Author
Eric Brown - Nebulock, Inc.
Source
github.com/Nebulock-Inc/macos-coresigma

Detect logs from securityd indicating code signature failures which might reflect tampering.

Rule body yaml

title: macOS ULS securityd CodeSignature Failure
id: e1c4dc0e-3a75-4f58-8e8f-5d4a9f9a1b2c
status: experimental
description: Detect logs from securityd indicating code signature failures which might
  reflect tampering.
author: Eric Brown - Nebulock, Inc.
date: 2025-10-29
logsource:
  product: macos
  service: unifiedlog
level: medium
detection:
  selection:
    subsystem: com.apple.securityd
    message|contains:
    - code signature invalid
    - rejecting
  condition: selection
falsepositives:
- developer builds or ad-hoc signing
modified: 2025/01/15

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
  subsystem: com.apple.securityd
  message|contains:
  - code signature invalid
  - rejecting

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
messagematch
  • code signature invalid
  • rejecting
subsystemeq
  • com.apple.securityd