Hackers love a challenge.
Computer security experts do as well. Firewalls, like those developed by Secure Computing and IBM, were once thought to be enough protection to ward off phreaks. But hackers became wise to their ways. Then proxy servers, offered by Microsoft Corp., and others, emerged. The VPN functionality is added to the servers of ISPs in the i-Pass alliance, a group of ISPs and telcos operating about 1,300 points of presence in 150 countries.