If you think your latest Twitter follower is a spammer, you are probably correct. If the Twitterer in question following hundreds or thousands of people, but has few followers, it's probably a spammer. If every tweet includes a brief sales pitch and a link, it's probably a spammer. If the account is the name of a cutesy girl and a pornographic profile picture, it's probably a spammer.
It is not particularly difficult to identify a spammer Twitter, but chances are there other things you would rather do with your time. Topify is a new application that puts more information in your Twitter notifications, making it faster and easier to block spammers. TwitChuck and uses a variety of methods to help you avoid, unfollow, block and report spam accounts.
Many Twitterers judge polite to follow anyone who follows them. But when you follow a spammer, you encourage the practice and make a disservice to all legitimate users Twitter. And when you block a spammer, you make it easier for Twitter to find and delete the account, and therefore a favor to all legitimate users Twitter.
Like other spammers, Twitter spammers are trying to push a product or lure victims to a phishing site, or deceive in malware download, or they may be trying to build a mailing list they can sell. They can be a simple discomfort, or they can be pirates or dangerous identity thieves.
So beware of spam on Twitter or elsewhere. And make sure to protect your computer against malware and phishing sites with Internet security software.