I created maintenance backups to save the databases daily, before this I was doing it manually... I lost some information but luckily I had a backup almost up to date....
Guys, it's confirmed, the site was hacked. I found a new user in the admin tables. The problem of this site is that I don't have any "manage users" section...
Thanks Steve, I'm going to read it right now. I use stored procedures and parameters always, and I think I do things properly but I don't know what is inside...