Wirehog was a friend-to-friend file sharing program that was linked to Facebook and allowed people to transfer files directly between computers.

It was created by Andrew McCollum, Mark Zuckerberg, Adam D'Angelo, and Sean Parker during their development of The Facebook social networking website in Palo Alto in the summer and fall of 2004. The only way to join Wirehog was through an invitation from a member and although it was originally planned as an integrated feature of Facebook, it could also be used by friends who weren't registered on Facebook. Wirehog was originally launched in October 2004 and was taken down in January 2006. Its target audience at the time was the same as the campus-only file-sharing service i2hub that launched earlier that year. i2hub was gaining a lot of traction and growing rapidly. In an interview with The Harvard Crimson, Zuckerberg said, "I think Wirehog will probably spread in the same way that thefacebook did."

The software was described by its creators as "an HTTP file transfer system using dynamic DNS and NAT traversal to make your personal computer addressable, routable and easily accessible". The client allowed users to both access data stored on their home computer from a remote location and let friends exchange files between each others computers. In ways, Wirehog was a project comparable to Alex Pankratov's Hamachi VPN, the open-source OneSwarm private network, or the darknet RetroShare software.