It's a matter of doing things that would be impossible to do without it. A ccessibility is both the Web's greatest promise and its greatest threat. The challenge, for anyone building a business Web site, is to achieve a reasonable level of security without impeding opportunity. And every organization will have to weigh its individual goals against a variety of costs.
Security can be expensive.
It can slow down performance. So when it comes to building a security system that fits the needs of a particular site, few of the answers come easy. That's how you decide how much security should be implemented per application . As for estimating cost, Elledge says it's hard to cite a certain percentage of a Web budget that should be allocated to security needs. Still, he suggests that 10 to 15 percent isn't out of line.