Web application security describes security methods applied to Web servers, Web applications, and application users. Examples of Web applications include online banks, shopping, auction sites, and Web-hosted e-mail. Examples of Web application security include authenticating user access to an online bank, protecting and validating cookies used by an auction site to maintain user state and privacy, or validating all user-supplied input before it’s processed by the Web application. Since Web applications reside in the application layer, the terms “application security” or “application firewall” are typically used interchangeably with Web application security.