Friend got hacked!!!!

First things first monday wasn't bad it bad at all it was pretty good. But to the title, one of my friends was hacked and the person who did it was really bad, I'm talking like really bad stuff about my gf. It was really bad and he said it to a bunch of other people so we were all mad at him cause we thought it was actually him. I was relieved to find out that it wasn't him otherwise I would of had to beat him up :) not really but I would have my gf beat him up lol inside joke, anyways i would verbally beat the words out of him :) or use violence whichever was more necessary.