Screenshot by Lance Whitney/CNET

A lot of Facebook users seem to be in the dark over how to protect their private information.

Out of the 150 million Facebook users in the U.S., almost 13 million don't use or aren't aware of the site's privacy settings, according to a report published in the June issue of Consumer Reports. Further, 28 percent of the people polled by CR shared all, or almost all, of their wall posts with people beyond their friends.

Consumer Reports uncovered other types of risky behavior among Facebook users.

An estimated 4.8 million people have posted details about where they plan to go on a specific day. Such a tip-off can attract burglars who can find a person's address and know when the house will be empty. Incidents have already occurred in which criminals have robbed homes based on information posted on social networks.

The study also found that 4.7 million people have "liked" a certain Facebook page about health conditions or treatments, which CR believes insurance companies could use against them.

Even those who batten down their privacy could be at risk, noted Consumer Reports.

As one example, people who limit their personal information to be seen only by friends could potentially find their data exposed to third parties if a friends shares it via a Facebook app.

Some people are going so far as to post phony information because of security concerns. CR found that 25 percent of the people polled said they falsified certain details in their profile to protect themselves, up from just 10 percent a couple of years ago.

Beyond doctoring their data, how can Facebook users protect themselves and their online identites?

The magazine offers a variety of suggestions, among them:

Think before you type. Even if you delete your Facebook account, certain information can stick around for as long as 90 days.

Review your privacy settings on a regular basis and see how your own page looks to other people.

Protect basic information, such as your town or employer. And remember that sharing certain details with "friends of friends" could expose you to a lot of people.

Your username and photo are public, so users concerned about privacy may want to leave out a picture of themselves.

Set your controls to limit the information that Facebook apps can see about you.

To compile its report, Consumer Reports surveyed more than 2,000 households, of which 1,340 were active on Facebook. The magazine also reached out to Facebook for information as well as to security experts, privacy attorneys, and victims of privacy abuse.