Hide Artifacts: Resource Forking

Adversaries may abuse resource forks to hide malicious code or executables to evade detection and bypass security applications. A resource fork provides applications a structured way to store resources such as thumbnail images, menu definitions, icons, dialog boxes, and code.[1] Usage of a resource fork is identifiable when displaying a file’s extended attributes, using ls -l@ or xattr -l commands. Resource forks have been deprecated and replaced with the application bundle structure. Non-localized resources are placed at the top level directory of an application bundle, while localized resources are placed in the /Resources folder.[2][3]

Adversaries can use resource forks to hide malicious data that may otherwise be stored directly in files. Adversaries can execute content with an attached resource fork, at a specified offset, that is moved to an executable location then invoked. Resource fork content may also be obfuscated/encrypted until execution.[4][5]

ID: T1564.009
Sub-technique of:  T1564
Tactic: Defense Evasion
Platforms: macOS
Permissions Required: User
Defense Bypassed: Notarization; Gatekeeper
Contributors: Ivan Sinyakov; Jaron Bradley @jbradley89
Version: 1.0
Created: 12 October 2021
Last Modified: 16 October 2021

Procedure Examples

ID Name Description
S0276 Keydnap

Keydnap uses a resource fork to present a macOS JPEG or text file icon rather than the executable's icon assigned by the operating system.[6]


ID Mitigation Description
M1013 Application Developer Guidance

Configure applications to use the application bundle structure which leverages the /Resources folder location.[7]


ID Data Source Data Component
DS0017 Command Command Execution
DS0022 File File Creation
File Metadata
DS0009 Process Process Creation

Identify files with the com.apple.ResourceFork extended attribute and large data amounts stored in resource forks.

Monitor command-line activity leveraging the use of resource forks, especially those immediately followed by potentially malicious activity such as creating network connections.