First, I will give an explanation of what SSH'ing is, and why you should know how to do it. SSH (Secure Shell) allows you to exchange data between two networked devices, using a secured channel. A jaibroken iPhone has the ability to transfer data to and from your computer via SSH, giving you complete access to the iPhone's hard drive.
Access to your iPhone's hard drive give you unlimited control, from fixing broken files, to installing games that aren't in the App Store, to turning your phone into a portable HDD. Sounds complicated, but it's very simple with the use of SSH clients like WinSCP (Windows) and Cyberduck (Mac).
Obviously your iPhone will need to be jailbroken, a simple Google search will help you find out how.
Step 1: Download an SSH Client relevant to your operating system.
Step 2: On your iPhone, open ‘Cydia.app’ and do a search for ‘OpenSSH’. Go ahead and install it, and jump back on your computer.
Step 3: Open the Cyberduck application we downloaded earlier and click the ‘Open Connection’ button.
Step 4: In the server field you are going to type your iPhone’s IP address. This can be found by launching your ‘Settings.app’, selecting ‘Wi-Fi’, and selecting the blue arrow next to your wireless network. You should now see your IP address.
Step 5: Select the ‘SFTP’ option in the drop down menu above where you just typed in your IP address.
Step 6: In the Username field type in ‘root’. In the Password field type ‘alpine’. Click connect! Viola!
Note: The first SSH may take a little longer, after that it should be fine. If you get an ‘Unknown Host’ message, just ignore it and click ‘Allow’.
Always back up any file you choose to delete, edit, etc. It could have negative effects on your iPhone.