Micro-blogging site Twitter is fast being swamped by spammers carpet bombing users with the usual questionable adverts.

Part of the problem is that users automatically follow people who follow them, normally out of being polite. Now according to Christopher Peri, CEO of Twitfilter, a Web-based app that helps manage income tweets and Twitter followers, the situation is about to get a lot worse.

Spammers are getting more sophisticated and are starting to use keywords and target specific users, and unload messages into users’ timelines. Currently one in ten posts is spam and the figure is going to get a lot worse, Peri claims.

So while users can take steps to limit spam, what is Twitter doing about  it? Well it has a problem because some spam is at the request of users. They have signed up for regular updates from companies on price cuts and bargains.

So if Twitter just filtered spam which included phrases like “buy now” or “make your penis the size of Texas” it might anger some users who want that sort of spam.