Instant messaging spam will triple this year alone, according to research firm Radicati Group.

Currently running at 400 million a year, 2004 will see an incredible 1.2 billion bits of unsolicited, and usually unwanted, mail delivered by IM.

The increase in IM spam - which some misguided linguists are trying to label "spim" - is thanks to far greater use of the technology by business, and a rapid increase in published IM names in corporate and public directories, Radicati said in a report.

The overall business IM market grew by 130 percent between 2002 and 2003, and a further 85 percent from 2003 to 2004, according to another research company, Ferris Research. By 2007, the overall business IM market will increase to 182 million users - a compound annual growth rate of 79 percent.

But just as e-mail spam has made the communication medium increasingly irritating, IM spam threatens to do the same. IM spammers are developing sophisticated software which automatically sends messages - mainly touting pornography - to millions of users, and which can automatically change screen names when the user blocks an IM attempt, according to Ferris.

Because of the intrusive nature of IM, such spam is likely to be both more annoying and more successful, Ferris added. Currently, efforts to tackle the spam problem are focused on the email problem but there are some groups already working on IM equivalents.