Greasemonkey is a Firefox extension that basically allows you to write JavaScript scripts that make on-the-fly changes to web pages you visit. As the scripts are persistent, the changes made to the web pages are executed every time the page is opened.

So what do these scripts do? Almost anything. Greasemonkey can be used for adding new functionality to web pages, fixing bugs, retrieving data from other web sites and combining them together and so on. If you’re a big fan of Greasemonkey and a security-conscious Internet user, this hack is just for you.

GMail Encrypt - GMail Encrypt is a user script that adds encryption to the emails you write in GMail. It uses RSA encryption and offers an online utility for producing the public and private keys needed for encryption. Download GMail Encrypt here.

Secure Site Passwords - Everyone has too many passwords to remember. Most people just give up and use one password everything. But we’re talking about security, ain’t we? Secure Site Passwords is a personalized system of generating passwords locally and retrieving them on demand (just like Keychain or Firefox’s master password).

This Greasemonkey script lets your define a local master password that you enter for each web site you visit. The password is not stored on the hard disk. You just enter it whenever you need to access a password-protected web site. Download Secure Site Passwords.

Allow Password Remembering - This Greasemonkey script runs on all pages and disables any auto complete attribute on an HTML element, so that you can decide which password the browser should save. Download Allow Password Remembering.

Google Secure - Although Google offers secure connections over SSL (Secure Socket Level) to their web services, they don’t really encourage it. If you want to protect your private data from prying eyes, use this Greasemonkey script to force secure connections to Google web services. Download Google Secure.

Google Cookie Cleaner - Don’t want Google to track your searches? This user script simply removes Google’s cookies from your computer. Download Google Cookie Cleaner.