Internet Security Program? You need to be a little clearer on this as it can cover many applications. If you mean Firewall wise, the best two I know of (when I used to be up-to-date with Firewall ratings and so forth) were Sygate and Kerio. But then again I haven't read up on any firewall ratings / reviews in a while so there may Indeed be better ones that I'm sure other people will suggest
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Of course I would like to say that for even greater security, there is nothing like having a hardware firewall as well as a software for double the protection. Routers with built in firewalls prove very effective against malicious attacks etc.
Hope this helps.
Breaks.