🛡️ Gatekeeper & XProtect
Safe install defaults + how to handle blocked apps
Gatekeeper helps block untrusted apps from running, and XProtect helps detect known malware. This guide shows the safest defaults to keep enabled and a safe workflow for handling an app that macOS blocks.
đź’ˇ What This Guide Covers
We focus on the “download → first run” protection chain: Gatekeeper checks, notarization/signature signals, and safe user decisions when a block dialog appears.
How It Works (High Level)
1 Download-to-run security pipeline
This diagram shows what macOS checks when you try to run an app for the first time.
2 Roles: Gatekeeper vs XProtect vs MRT
These are different layers that can block or remediate malware at different times.
Recommended Default Configuration
3 Keep “Allow applications from” set to safest default
- System Settings → Privacy & Security → Allow applications from
- Recommended: App Store & Known Developers
When macOS Blocks an App
🚨 Safety Rule
If you do not trust the source, do not bypass Gatekeeper. The “Open Anyway” override is a common way malware gets installed.
4 Unidentified developer block dialog
This is one of the most common Gatekeeper warnings.
If you see this, the safest response is to cancel and obtain the app from a more trusted source.
5 Understand why you’re blocked
Use this decision tree to interpret the common block reasons.
6 Notarization (simplified)
This shows the basic idea: developer signs → Apple scans (notarization) → macOS verifies.
7 “Apple can’t check app for malicious software” guidance
This official guidance explains the risks of overriding security settings.
8 Safe override path (only if you trust the source)
If you must override, use the official “Open Anyway” flow and do it intentionally.
