Detection rules › Sigma

macOS ULS Potential TCC Bypass Indicators

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

Detect logs referencing TCC errors or denials that might indicate attempts to bypass privacy controls.

Rule body yaml

title: macOS ULS Potential TCC Bypass Indicators
id: d5a8a3c7-58a6-4a8a-9e07-4ad7a0e6ec0a
status: experimental
description: Detect logs referencing TCC errors or denials that might indicate attempts
  to bypass privacy controls.
author: Eric Brown - Nebulock, Inc.
date: 2025-10-29
logsource:
  product: macos
  service: unifiedlog
level: medium
detection:
  selection:
    message|contains:
    - TCC
    - kTCCService
    - access denied
    - prompting for access
  condition: selection
falsepositives:
- noisy applications frequently requesting sensitive entitlements
modified: 2025/01/15

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
  message|contains:
  - TCC
  - kTCCService
  - access denied
  - prompting for access

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
  • TCC
  • access denied
  • kTCCService
  • prompting for access