Your credit report will tell you who else has been viewing your credit report. Called "inquiries" in credit-speak, they come in two kinds.
Hard inquiries are when you have actually requested new credit -- filled out an application, signed paperwork, etc. -- and asked a lender to check your history. When you get a hard inquiry, your credit can take a small dip. Hard inquires could affect your score for one year, but you'll see them on your report for two years.
Soft inquiries are what credit bureaus put on your report when someone reviews your credit file but you haven't asked for new credit. If you pull your own credit report, that's a soft inquiry. You'll also see one if a prospective lender pulls your credit for marketing purposes. Soft inquiries don't affect your score.
Hard inquiries are "such a small part of your credit score," says Kelly Rogers, chief development officer for the nonprofit Consumer Credit Counseling Service of Orange County, Calif., and adjunct faculty at Chapman University. "But it's such a great way to see if anyone's been using your information."