The information is compiled from phone books, property records, court documents, government databases and other sources. Various companies buy and sell this data without your permission or knowledge.
The problem (besides the violation of your privacy) is that these records are very likely to contain errors.
Somewhere between 10 percent to 50 percent of the records on any given person contains errors, according to my own research. Sometimes it's a minor thing that can make it appear as if you're lying -- such as an error in your age, for example. Other times it's major -- false information that suggests you have bad credit or a criminal record.
Many of these databases confuse one person with another, so an employer might choose not to hire you based on a background check on a total stranger with the same name.
That's why it's important -- vital if you're planning to job hunt anytime in the near future -- to find out what false information is floating around out there about you. By knowing what the errors are, you might be able to correct them at the source, or at least warn checkers about false data.
Don't think nobody will check. Even employers who don't conduct such checks as a matter of policy may do so anyway. There is nothing to stop a hiring manager from personally going online and running a check. It's easy, fast and cheap -- and totally anonymous for the manager.
The first thing you should do -- right now -- is understand how easily available your personal information is. In thirty seconds, I'm going to show you the following data about yourself: Your age; current and past addresses; current and past phone numbers; and the names of your immediate relatives (spouse, children and possibly parents). Go to here and here and search for your first and last name (don't use middle initial) in both search engines.
Shocked? That's just the beginning. For a few dollars, people can find out your criminal record, bankruptcy and lien history, everything you've ever done in a courtroom, your educational and work history, who your friends and relatives are, where you've lived, the value of your home, your credit details and more.
The chance that all this information is error-free is close to zero. You need to check.
Here are the best search engines for finding out what information people can find out about you.
PeopleData PeopleData feels like a Google search, and returns individual hits for each record, rather than one collective result. For example, if you've lived in three cities, it will return one hit from each city. The hit itself will usually give you the address or, less often the phone number. This is very rare among people search engines -- usually they make you pay to see the address-- but when you click on the link, it often takes you to another service that often doesn't know you at all. PeopleData is the best search engine for finding out addresses, birthdates and phone numbers without paying anything.
PeopleLookup.com PeopleLookup presents you with free information about who your relatives are, your age and other info, then links you to for-pay deep-searches.
WhitePages.com This service is better than most, and may drudge up records the other search engines don't. It links to high-quality, for-pay deep searches.
Peoplefinders This is the newest search engine of the lot. It provides an innovative instant search capability, so you can really refine searches in real time.
US Search This is very accurate and complete, but you'll need to pay.