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 (Citation: Mac Backdoors are back).Adversaries can use this feature to trick users into double clicking benign-looking files of any format and ultimately executing something malicious.
Space After Filename
Supported Platforms: macOS
-
echo '#!/bin/bash\necho "print "hello, world!"" | /usr/bin/python\nexit' > execute.txt && chmod +x execute.txt
-
mv execute.txt "execute.txt "
-
./execute.txt\