We're using Trendmicro AV (ServerProtect for NT/Netware server, Officescan for PCs, Interscan for mail gateway and Scanmail for mail servers)
Network based and connection, tapos ung AV server ay may internet connection for auto-update/download ng virus pattern and engine. Then ung mga workstations automatic update din once new pattern/engine is available from the server.
Norton Antivirus 2000, I update at least once a month unless, I feel I need to update. I just hacked my update because my 2000 is way passed its "free" update na.
I full scan at least every month, unless I feel that my computer is infected.
I also use the free edition of AVG. So far so good. I also like the update method of AVG. If you are a frequent updater, you'll only need to download an ave. of 100k per update.
How about SPYWARE protection software?
I use both SPYBOT Search & Destroy and AdAware.