HTTP Strict Transport Security (HSTS)

1. Introduction

HTTP Strict Transport Security (HSTS) is a web security policy mechanism that helps protect websites against man-in-the-middle attacks such as protocol downgrade attacks and cookie hijacking. HSTS instructs browsers to only interact with the server using secure HTTPS connections.

2. Key Concepts

• HSTS allows web servers to enforce secure connections.
• It is implemented via a special response header sent by the server.
• Once a browser receives the HSTS header, it will refuse to connect to the site using HTTP.

3. Implementation

To implement HSTS, the server must send the following HTTP header:

Strict-Transport-Security: max-age=31536000; includeSubDomains

In this example:

• max-age=31536000 specifies that the browser should enforce HSTS for 1 year (in seconds).
• includeSubDomains applies this rule to all subdomains of the current domain.

Example of a server configuration for HSTS in Apache:

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

4. Best Practices

• Always test your HSTS implementation in a safe environment before going live.
• Use the preload directive to submit your site to browsers for inclusion in their HSTS preload lists.
• Regularly review and update your HSTS policies.

5. FAQ