Chances are your business doesn't employ a full-time spam administrator, which isn't to say you and your computers couldn't benefit from one. The onslaught of unsolicited bulk electronic messages-both email and blog comments for those who maintain blogs-threaten the productivity of real estate pros who can get bogged down screening and deleting junk communications. Spam is also a leading source of computer viruses which can bring your operations to a halt if you're not careful.

The growing onslaught can make spam prevention seem like an unwinnable. Spammers sent a record 100 billion messages around the world last year, according to Google, with the total volume growing by 1.2% every day. For small businesses, the unwanted e-mail slows down computer servers, potentially delaying all incoming and outbound messages.

Ferris Research, an information technology consulting company based in San Francisco, says that spam and related computer viruses cost U.S. businesses $42 billion last year in lost productivity. But there are steps you can take to reduce, if not eliminate, your vulnerability.