Https connections are often used to transfer important data, such as passwords, PINs, or credit card numbers. The browser ensures that the sender can be identified with a valid certificate and that the transferred data are encrypted. An error in the Debian Linux distribution has generated numerous certificates that are child's play to crack. Many servers still use these weak certificates, even though it is impossible to establish a secure connection using them. The heise SSL Guardian checks the SSL certificates and warns you when it detects a weak one.