Random permanent ban???

I haven't played a game in a around a year. I tried to re-download League of Legends and I tried to log into my account and my account had been "permanently banned for the use of prohibited third party software." I never used any hacks or anything like that and I haven't played in a long time so maybe its a bug or something... I would really appreciate the help anyone has to offer because I need my account back.

Edit: maybe I got hacked while I was gone?