[chmod]

In short it's an automation script for bash (Linux) to inject shell code, in this case a meterpreter shell into a legitimate windows executable and then attempts to encrypt that data to bypass antivirus software allowing the code to executed on the remote machine giving the attacker full control of their system.

The script itself gathers information from the user about the configuration of their network and then passes that information on to the metasploit framework which injects the code and then crypts it giving you a new malicious (backdoord) .exe