OSX/Jahlav-A is a Trojan created for the Mac OS X operating system. The initial malicious installer is distributed to free downloading web sites purporting to be a key generator for cracking applications.
As a part of the installation a malicious shell script file AdobeFlash is created in /Library/Internet Plug-Ins folder and setup to periodically run. The script contains another shell script in an encoded format which in turn contains a Perl script with the main malicious payload.
The perl script uses http to communicate with a remote website and download code supplied by the attacker.