Discovered in September 2014, Shellshock is a recent vulnerability in Unix Bash shell (Bash is a Unix shell and command language and is widely used by server deployments, computers, and such) that has spread across the globe at incredible speed. Security companies recorded millions of attacks in the days following the vulnerability disclosure. Shellshock was labeled as a very severe bug and was compared to the Heartbleed security bug that was disclosed in April 2014. If you've heard of Heartbleed, you probably know that this was a huge boom when it was discovered. Exploiting this vulnerability let anyone on the Internet encrypt the traffic, including names, passwords, and the actual content going through a connection.

The Shellshock bug is an example of an arbitrary code execution vulnerability. This term describes an attacker's ability to execute any commands on a target machine. It is the most powerful effect a bug can have because it lets an attacker take control over the target...