As Twitter has been getting more and more popular, it is increasingly targeted by spammers and account hijackers.
If you want to detect and eliminate them from your account, there is a quick and easy way. TwitBlock is a free online service that offers an anti-junk filter and a blocking tool for Twitter users.
It lets you scan your Twitter account (required log-in) for detecting spammers and block them. And also you can analyze any account to determine whether it is spam or not.