Good call. There`s rarely any need for most users to be installing from outside the repositories, especially stuff that`s already in there.
Read the
security sticky over on Ubuntu forums. It should give you a better understanding of things to help you decide whether you might want/need AV or not.
Personally i`ve never used it and indeed never needed it in the nigh on 4 years i`ve now used *buntu/Linux in one form or another.
Some other good practices you might like to consider.
1: Not messing about with any of the default settings with regard to networking and not opening all manner of ports to the outside world for the likes of vnc/ssh etc, not without learning how to secure them properly anyway.
2: Use strong passwords for all users.
3: Don't install software from untrusted sources.
4: Use the NoScript extension in Firefox.
5: Back up regularly
6, 7, 8, 9 & 10 Don't be dumb. You only have to visit the security section of UF to see dumb people getting themselves hacked left, right & centre.
