There are also hundreds of online address books that contain information on you, some of which surely won't be accurate. For US$5 a month, Reputation Defender offers a service called MyPrivacy that locates your listings in some of the major Internet white pages and lets you remove your data. At press time, though, the service--a beta--was still buggy and incomplete. (See item #5 for another Reputation Defender service.)

And don't forget Wikipedia. You may have a false or defamatory entry in the world's most popular online encyclopedia and never know it. In the most infamous case, retired journalist John Siegenthaler publicly outed the encyclopedia for a false entry that implied he played a role in the Kennedy assassinations. If you've got a Wiki page and want to keep it, you'll need to keep an eye out for erroneous edits.

3. Opt Out Early and Often

By reducing the amount of junk mail you receive, you make yourself a smaller target for identity thieves and others who can mess with your reputation. (One of identity thieves' favorite tricks is to sign up for a change of address in your name, so they can re-route pre-approved credit card offers to your "new address.")

Though there's almost no way of getting your junk quotient down to zero, taking your name off marketing lists will nuke 50 to 75 percent of it. The easiest way? Sign up for ProQuo. This free service can help delete your name from more than a dozen marketing lists--including those operated by the Direct Marketing Association and massive data brokers like ChoicePoint and Acxiom.

In some cases ProQuo will remove your name for you; in other cases it directs you to the opt-out page for an organization's Web site or gives you sample letters that you must print out, sign, and mail. You can also use ProQuo to tell Equifax, Experian, and TransUnion to stop selling your information to companies that send you pre-approved credit card offers, and to thwart telemarketers by adding your name to the FTC's Do Not Call list. ProQuo is dead simple to use, and there are no strings attached.

4. Do Your Own Background Check

There is a treasure trove of information about you freely available to anyone who knows how to look for it. Do you own property? Are you licensed to carry a concealed weapon? Have you ever been late with your tax payments? Arrested? Divorced? In most states, that information is in the public record, and much of it is available online for a fee. When an employer does a background check on you, this is the kind of stuff that turns up--so at the very least you want to make sure the information is accurate. Fortunately, you can request a free public records report from ChoicePoint. (You'll have to print out a form and mail it along with copies of your driver's license and proof of address.)

While you're at it, order your free annual report from the big three credit bureaus. This information shows up when you try to open a new credit account, buy a mobile phone, rent an apartment, or apply for a job, among other things. Unfortunately, credit reports are notoriously inaccurate. A 2004 study by the US Public Interest Research Group found that one in four reports contains an error serious enough to deny you credit or employment. So you'll want to review and correct them as needed.

And be careful who you order your report from. The vast majority of sites that advertise "free credit reports" try to trick you into signing up for credit monitoring services at US$10 to $15 a month. The right place to go is AnnualCreditReport.com.