Identity theft definition
Identity theft is the use of someone else's personal information without permission, typically to conduct financial transactions. By personal information, we mean data that institutions use to identify or recognize you: your social security number, your bank account number, your address history, and so forth.
These sorts of data points are in theory private but in practice can often be discovered in a variety of ways by a dedicated identity thief, who can then either access your own accounts or open new ones in your name. The latter practice can be particularly pernicious: with just your social security number, identity thieves can take out loans or credit cards that they never pay off — and the resulting damage to your credit rating can be very difficult to undo.