Loosely-defined, click fraud occurs when an Internet ad is clicked upon for nefarious reasons, such as driving up a business competitor's ad costs. The practice takes advantage of how Internet advertisers pay a small fee to Google and other Internet ad providers each time one of their ads is clicked upon.

Some click-fraud-fighting companies believe the practice is rampant, forces advertisers to pay an extra $16 billion a year, and that up to half of all ad clicks are fraudulent.

But according to Google , in the worst cases, on average 10% of all ad clicks are invalid. Typically, the amount is in the low-single-digit percentages. Google bases that figure on the average number of invalid clicks that it catches, and as a result, doesn't charge customers for.

That amounts to about $1 billion a year in payments Google could have collected, but chose not to, it said.

The amount of click fraud Google doesn't catch, but is brought to its attention by advertisers, represents less than 0.02% of the times an ad's clicked upon, according to Google.

The information Google released Thursday does not present a complete picture. What's missing is the number of fraudulent clicks that Google doesn't catch. But what Google released Thursday is the most complete picture to date the company has offered.

Get the full story at CBS MarketWatch