source command loads functions into the current shell or executes files in the current context. This built-in command can be run in two different ways
source /path/to/filename [arguments] or
. /path/to/filename [arguments]. Take note of the space after the ".". Without a space, a new shell is created that runs the program instead of running the program within the current context. This is often used to make certain features or functions available to a shell or to update a specific shell's environment.
Adversaries can abuse this functionality to execute programs. The file executed with this technique does not need to be marked executable beforehand.
Due to potential legitimate uses of source commands, it's may be difficult to mitigate use of this technique.
Monitor for command shell execution of source and subsequent processes that are started as a result of being executed by a source command. Adversaries must also drop a file to disk in order to execute it with source, and these files can also detected by file monitoring.