Is that free wifi you're surfing on at the airport or the coffee shop really secure? Forbes reports there's a nearly 75% chance that it's not.

The single worst location for wifi compromises was Newark Airport. Out of all the networks they scanned in that particular airport, only 9% of them were secure. See Forbes' complete tally of results for some of the nation's most popular airports.

So what can you do about it? Simple -- don't under any circumstances visit the website of your bank, credit union and brokerage house or mutual-fund company when using a free wifi connection while you're out and about. The risk is just too great.