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Gatekeeper Bypass

In macOS and OS X, when applications or programs are downloaded from the internet, there is a special attribute set on the file called This attribute is read by Apple's Gatekeeper defense program at execution time and provides a prompt to the user to allow or deny execution.

Apps loaded onto the system from USB flash drive, optical disk, external hard drive, or even from a drive shared over the local network won’t set this flag. Additionally, other utilities or events like drive-by downloads don’t necessarily set it either. This completely bypasses the built-in Gatekeeper check. [1] The presence of the quarantine flag can be checked by the xattr command xattr /path/to/ for Similarly, given sudo access or elevated permission, this attribute can be removed with xattr as well, sudo xattr -r -d /path/to/ [2] [3]

In typical operation, a file will be downloaded from the internet and given a quarantine flag before being saved to disk. When the user tries to open the file or application, macOS’s gatekeeper will step in and check for the presence of this flag. If it exists, then macOS will then prompt the user to confirmation that they want to run the program and will even provide the URL where the application came from. However, this is all based on the file being downloaded from a quarantine-savvy application. [4]

ID: T1144
Tactic: Defense Evasion
Platform: macOS
Permissions Required: User, Administrator
Data Sources: File monitoring, Process command-line parameters
Defense Bypassed: Application whitelisting, Anti-virus
Version: 1.1
Created: 14 December 2017
Last Modified: 25 June 2019

Procedure Examples

Name Description

CoinTicker downloads the EggShell mach-o binary using curl, which does not set the quarantine flag.[5]


Mitigation Description
Execution Prevention

System settings can prevent applications from running that haven't been downloaded through the Apple Store which can help mitigate some of these issues.


Monitoring for the removal of the flag by a user instead of the operating system is a suspicious action and should be examined further. Monitor and investigate attempts to modify extended file attributes with utilities such as xattr. Built-in system utilities may generate high false positive alerts, so compare against baseline knowledge for how systems are typically used and correlate modification events with other indications of malicious activity where possible.