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T1036.006 Space after Filename

Adversaries can hide a program’s true filetype by changing the extension of a file. With certain file types (specifically this does not work with .app extensions), appending a space to the end of a filename will change how the file is processed by the operating system.

For example, if there is a Mach-O executable file called evil.bin, when it is double clicked by a user, it will launch Terminal.app and execute. If this file is renamed to evil.txt, then when double clicked by a user, it will launch with the default text editing application (not executing the binary). However, if the file is renamed to evil.txt (note the space at the end), then when double clicked by a user, the true file type is determined by the OS and handled appropriately and the binary will be executed 1.

Adversaries can use this feature to trick users into double clicking benign-looking files of any format and ultimately executing something malicious.

Item Value
ID T1036.006
Sub-techniques T1036.001, T1036.002, T1036.003, T1036.004, T1036.005, T1036.006, T1036.007, T1036.008, T1036.009, T1036.010, T1036.011, T1036.012
Tactics TA0005
Platforms Linux, macOS
Version 1.1
Created 10 February 2020
Last Modified 24 October 2025

Procedure Examples

ID Name Description
G0082 APT38 APT38 has put several spaces before a file extension to avoid detection and suspicion.3
S0276 Keydnap Keydnap puts a space after a false .jpg extension so that execution actually goes through the Terminal.app program.2

References

  1. Dan Goodin. (2016, July 6). After hiatus, in-the-wild Mac backdoors are suddenly back. Retrieved July 8, 2017. ↩

  2. Patrick Wardle. (2017, January 1). Mac Malware of 2016. Retrieved September 21, 2018. ↩

  3. SEONGSU PARK. (2022, December 27). BlueNoroff introduces new methods bypassing MoTW. Retrieved February 6, 2024. ↩