Space after Filename
Where this stands
One published detection covers this technique. Every one is unverified — no rule on Siemphony has been executed against real telemetry.
What the technique is
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. Adversaries can use this feature to trick users into double clicking benign-looking files of any format and ultimately executing something malicious.
Read it on attack.mitre.orgWhat MITRE says you would watch
- AN0812
Detection of file execution where the file name contains a trailing space to masquerade as a known executable. Adversaries may exploit the way command line interpreters handle file names with trailing whitespace.
- AN0813
Execution of renamed or dropped files with a trailing space to deceive users or analysts, especially in LaunchAgents or LaunchDaemons.
Technique names and descriptions © MITRE ATT&CK®, CC BY 4.0. Not endorsed by MITRE.