macOS Gatekeeper / Quarantine / XProtect
👉 Overview
👀 What ?
macOS Gatekeeper, Quarantine, and XProtect are built-in security features of Apple's operating system. Gatekeeper checks for the developer's ID and whether the app has been altered since it was signed. Quarantine tags downloaded files and alerts the user before opening them. XProtect is a malware scanner that checks files against known malware definitions.
🧐 Why ?
The importance of these features lies in their role in enhancing the security of macOS. They aim to prevent the execution of malicious software, alert users about potentially unsafe files, and safeguard the system against known threats. With the increasing number of cyber threats, every macOS user needs to understand these features to ensure they are leveraging their benefits fully for their system's security.
⛏️ How ?
These features are automatically enabled in macOS and need no manual configuration. However, you can further adjust security settings in System Preferences > Security & Privacy > General. For Gatekeeper, you can choose to allow apps downloaded from App Store or App Store and identified developers. Quarantine warnings can be bypassed by right-clicking a file and selecting 'Open'. XProtect updates silently in the background, but you can manually update it by updating your system software.
⏳ When ?
Apple introduced these features in different versions of macOS. Gatekeeper was first introduced in macOS Mountain Lion in 2012. Quarantine was introduced in macOS Leopard in 2009. XProtect was also introduced in 2009 with macOS Snow Leopard.
⚙️ Technical Explanations
macOS Gatekeeper, Quarantine, and XProtect are integral security features built into Apple’s operating system.
- Gatekeeper uses public-key cryptography to ensure an app's authenticity and integrity. When a developer signs their app, the app's contents are hashed, and this hash is combined with the developer's ID. The combination is then encrypted with the developer's private key to form a signature, which is embedded within the app. When you download the app, Gatekeeper decrypts the signature using the developer's public key and verifies the app's hash and the developer's identity. Gatekeeper helps protect against altered or tampered apps, and its settings can be adjusted in the Security & Privacy section of System Preferences.
- Quarantine is designed to protect users from potentially unsafe files downloaded from the internet. It attaches a special attribute ('com.apple.quarantine') to downloaded files. This attribute contains information about the file's download time and source. When you attempt to open a quarantined file, macOS checks this attribute and provides a warning about the file's origin. Although it's generally recommended to heed these warnings, they can be bypassed by right-clicking the file and selecting 'Open'.
- XProtect serves as a basic malware scanner. It uses signature-based detection to identify known malicious software. It has a list of malware signatures (stored in 'XProtect.plist') that it compares against files on your system. If a file matches a signature from the list, XProtect blocks it from opening. The list of signatures is updated periodically to stay up-to-date with new threats. These updates are done silently in the background but can also be manually triggered by updating your system software.
These features are automatically enabled on all macOS devices and collectively contribute to a safer and more secure user experience.
Here are detailed examples of how these security features work in macOS:
- Gatekeeper: When you download an app, say a photo editor from the App Store, Gatekeeper checks the app's digital signature. Developers sign their apps with a unique Developer ID and a private key from Apple. For example, if the developer's ID is 'Dev123', and the hash of the app is 'xyz', these are combined and encrypted to form a signature. This signature is embedded within the app. Gatekeeper decrypts the signature using the public key corresponding to 'Dev123' and verifies the hash. If the hash matches, the app is considered safe and is allowed to open.
You can see the Gatekeeper settings in macOS by going to 'System Preferences > Security & Privacy > General'. Here you can choose to allow apps downloaded from App Store or App Store and identified developers.
- Quarantine: When you download a file, say a PDF from a website, macOS automatically attaches a 'com.apple.quarantine' attribute to the file. This attribute contains the timestamp of the download and the URL of the download source. When you try to open the file, macOS warns you about the file's origin. You can bypass this warning by right-clicking the file and choosing 'Open'.
You can check if a file is quarantined using Terminal and the command ls -l@ [filepath]. If the file is quarantined, you'll see the 'com.apple.quarantine' attribute in the output.
- XProtect: XProtect works in the background and scans files against its list of known malware signatures. For example, if you download a file 'example.exe', XProtect checks whether this file's signature matches any in its 'XProtect.plist'. If there's a match, the file is blocked from opening.
You can manually update XProtect by updating your system software. Go to 'System Preferences > Software Update' and click 'Update Now' if there's an update available.