Most of the people reading this post were older than 13 years of age when Facebook was unleashed upon the world a few years back, so we never had to lie about our age just to play Frontierville or post grainy camera phone photos of ourselves. But according to a new study from our kin at Consumer Reports, more than one in three of the 20 million Facebook users under the age of 18 are also too young to actually be on the site in the first place.

In CR’s latest State of the Net report, the magazine not only finds that 7.5 million Facebook users are under the required age of 13, but that more than 5 million of these users are 10 and under and that — perhaps not surprisingly — their accounts were largely unsupervised by their parents.

“Despite Facebook’s age requirements, many kids are using the site who shouldn’t be,” says Jeff Fox, Technology Editor for Consumer Reports. “What’s even more troubling was the finding from our survey that indicated that a majority of parents of kids 10 and under seemed largely unconcerned by their children’s use of the site.”

Letting young children use Facebook and other social media without supervision opens up the door to a lot more than creepy online predators. There is malware that can easily be downloaded by click-happy kids, not to mention the threat of identity theft.

According to Consumer Reports’ survey of 2,089 online households across the U.S., one-third had experienced a malicious software infection in the previous year. The magazine estimates that malware cost consumers $2.3 billion last year and forced them to replace 1.3 millions PCs.

CR’s full State of the Net survey can be seen in the June issue of Consumer Reports.

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