6:00 PM -- It's a simple idea: Your company buys ads on Websites where prospective customers might be. Every time somebody clicks on the ad, you get a sales lead, and you pay the site's host a small fee. If you get lots of clicks, you pay more, but it's worth it, because you're getting more prospects, right?

Right. Unless the "clicker" is a bot. Or somebody paid to do the clicking. Or one of your fiercest competitors.

Click fraud, the practice of manually or electronically creating "clicks" on an advertising page, is a growing concern among everyone who does Web marketing. (See Click Fraud: What IT Should Know.) According to Click Forensics, which studies these things, about 14 percent of the clicks on Web advertisements are from bots or humans who are only trying to drive up the hit count. Among advertisers who are paying more than $2 per click, it's more than 20 percent.

Who would want to drive those numbers up? Publishers and search engines, for one. Yep, sites like Dark Reading get more money every time you click on an ad. Even though the penalties are stiff for a publisher who gets caught -- Google had to settle a class action suit in March for $90 million -- click fraud has got to be a temptation for any pay-per-click site (I confess that my wife clicks on my stories sometimes without reading them, just to make me look better, though I don't think she ever clicks on the ads).

If you're a small business, another dangerous group is the competition. Think about it: At $1 a click, it would probably take less than an hour to wipe out your rival's $1,000 monthly ad budget. It's another temptation that's tough to get out of your mind. (Do you know which industry has the most click fraud? The legal industry, according to one monitoring service. I can just imagine that law intern, sitting and clicking on an ad all day, and wondering when he's going to learn something about the law.)

There are lots of tools and services offered by publishers, search engines, and the click fraud monitoring vendors, but the bottom line is conversions. Is your Web ad getting people to do what it asks them to do -- download the white paper, fill out the subscription form, create an electronic shopping cart? If not, you might be a victim of click fraud, and you may want to ask the host site to block clicks from suspicious sources (or at least not bill those clicks to you).

If you don't, you may find that somebody's just clicked away your ad budget this month.

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— Tim Wilson, Site Editor, Dark Reading