A cookie (HTTP cookie) refers to a mechanism used by websites to store state information on a user's computer, helping servers recognize clients across multiple HTTP requests. HTTP, being a stateless protocol, inherently treats each request independently, returning identical responses to identical requests. Early implementations of HTTP were not designed to provide stateful interactions. However, as web applications evolved—particularly applications like online banking that require different responses before and after user login—there emerged a need to manage state information effectively. HTTP cookies were developed to address this challenge.
Cookies are small data records stored locally on a user's device by the web server. Typically, cookie data can include user-identifying information, timestamps of previous visits, or visit frequency indicators. When a user revisits a website with a previously stored cookie, that site can recognize the user and respond accordingly, facilitating customized and stateful interactions.
Scripts embedded within web pages can also access cookies, but this access is strictly limited to cookies associated with the same domain as the originating script—a security practice known as the "same-origin policy." However, vulnerabilities like Cross-Site Scripting (XSS) can allow attackers to bypass these limitations and illegitimately retrieve cookie information.
To mitigate risks associated with XSS and other web-based threats, deploying a Web Application Firewall (WAF) provides an effective defense layer, helping to detect and block malicious attempts to exploit vulnerabilities in web applications.
F5 offers robust WAF functionality through its F5 BIG-IP solutions, preventing attacks like XSS and securing cookie content against unauthorized access.