But like Fort Knox, doesn't matter how much security you have in place, if a user opens a door for someone, a hole in the security has been opened up. Regardless of how much you hammer in to your users about what to look for, it is those targeted spear phishing emails that users are most likely to fall prey to. The crook knows his audience and how to possible get that door opened just enough to slip something in.

There was a time that you had your firewall on your network's edge and that was good enough. Those days are gone. Now you need a firewall and Intrusion Prevention system at the network edge (even more options is better); firewall, antivirus, and intrusion prevention on your mail server; and firewall, intrusion detection, antimalware/antivirus on your workstation. This is why we are paying for Sophos AV.