Twitter has finally improved the security of its users' accounts.
The good news is that it is a simple system, although you will have to enable it manually.
To reduce the chances of someone hacking your Twitter account you need to first register a mobile phone number with your account.
Next, visit Settings; Account; and tick the Account security option (see below):
Twitter will send a text (SMS) message to your phone to verify that it can communicate with you.
If that works you will need to enter your normal Twitter password again to enable the extra security.
If you log out of Twitter, and then log back in, you will find that you cannot access your account yet. To progress you need to enter a code that has been sent to your phone.
It's worth noting that Tweetdeck and other applications will continue to have access to your account, regardless of this change. This would be a good time to review your Apps settings and revoke access to any unnecessary applications.