Understanding HTTP Strict Transport Security (HSTS) and the HSTS Preload List

In the ever-evolving landscape of web security, one term you may have encountered is HTTP Strict Transport Security (HSTS). HSTS is a crucial security feature that helps protect websites and their users from certain types of attacks. In this article, we'll delve into what HSTS is, why it exists, and how to use it effectively, with a particular focus on the HSTS preload list.

What is HTTP Strict Transport Security (HSTS)?

HTTP Strict Transport Security (HSTS) is a web security policy mechanism that helps to protect websites against protocol downgrade attacks and cookie hijacking. It allows a web server to declare that web browsers should interact with it using only secure HTTPS connections and never via unencrypted HTTP. When a website implements HSTS, it instructs web browsers to automatically convert all HTTP links to HTTPS and prevents users from bypassing the secure connection.

Why does HSTS exist?

The primary purpose of HSTS is to enhance web security by ensuring that communication between a web browser and a website occurs over a secure HTTPS connection. This mitigates the risks associated with various attacks, including man-in-the-middle attacks, where an attacker intercepts and possibly alters the communication between a user and a website. Before the introduction of HSTS, web applications were vulnerable to attacks that exploited the use of insecure HTTP connections. By enforcing HTTPS, HSTS significantly reduces the likelihood of such attacks, thereby enhancing the overall security posture of websites.

How to Use HSTS

Implementing HSTS involves configuring your web server to include the HSTS header in HTTP responses. The header specifies the maximum amount of time (in seconds) that a browser should remember to only access the site over HTTPS. Here's an example of how to implement HSTS in an Apache web server configuration:

vbnetCopy codeHeader always set Strict-Transport-Security "max-age=31536000; includeSubDomains"

In this example,

max-age=31536000

instructs the browser to remember the HSTS policy for one year (31536000 seconds), and

includeSubDomains

indicates that the policy applies to all subdomains as well.

The HSTS Preload List

While implementing HSTS on your website is essential, it may take some time for browsers to recognize and enforce the policy. To expedite the process and ensure maximum security, there's the HSTS preload list. The HSTS preload list is a list of websites that have requested inclusion in the browser's built-in list of sites that must only be accessed via HTTPS. Browsers, such as Chrome, Firefox, and Safari, regularly update this list, and once a website is included, the HSTS policy is enforced immediately for all visitors, even those accessing the site for the first time. To include your website in the HSTS preload list, you need to meet certain criteria and submit a request through the dedicated preload submission website (hstspreload.org). Once approved, your website's domain will be added to the preload list, providing enhanced security for all users.

Conclusion

HTTP Strict Transport Security (HSTS) is a critical security feature that helps protect websites and their users from various types of attacks. By enforcing the use of HTTPS connections, HSTS mitigates the risks associated with protocol downgrade attacks and cookie hijacking. To maximize the effectiveness of HSTS, website owners should implement it correctly and consider submitting their domains to the HSTS preload list for immediate and comprehensive protection. By doing so, they contribute to a safer and more secure browsing experience for everyone.