There are two types of filtering technologies - filter lists and software algorithms. Lists contain URL and IP addresses that are to be blocked. The lists are updated regularly and are examined by people to ensure correct categorization. Algorithms use heuristics to determine if the page should be blocked, and therefore have higher error rate than filter lists. For ISPs, network software utilizing filter lists is the simplest, most accurate, and most manageable solution, as it only needs to be deployed at the data center.
Client software needs to reside on all clients' systems.
Companies like Secure Computing and N2H2 make filtering tools that let ISPs configure and manage Internet Web access policies for both individual customers and corporations. Further, most caches allow an ISPs' customers to apply their own filter lists, if their access needs are different from the standard categories provided through a third party's filtering application. Incorporated All Rights Reserved.