Privacy Alerts - Magnetic Strips

What's on the magnetic strip of my card? What information is stored on ATM, credit, driver's license, or other cards?

The dark strip on your ATM, credit, driver's license, and other cards is used to store information regarding you and your company account. It's actually magnetic and made of small iron-based particles on an additional magnetic material.

Basically, the orientation of the iron particles is translated into personal information when they are swiped across a reader head. (A reader head is just one of those machines they swipe your card through.)

There are two main types of strips: high coercivity and low coercivity . Low coercivity strips are the light brown strips you see on metro tickets, concert tickets, and train tickets. They are more sensitive to magnetic fields and can be demagnetized with weak fields or brief exposure to strong fields. In fact, a recent problem has been the demagnetization of metro/subway tickets when they are stored in the same pocket as an iPod Video (which creates a weak magnetic field from the spinning hard disk).

A high coercivity stripe is the dark brown or black strip you see on common forms of identification: credit cards, driver's licenses, ATMs, and the list goes on... These types of strips are pretty much resistant to the majority of magnets that are owned by people in the real world (that is, the non-industrial world).

Magnetic StripFor financial cards, the magnetic strip codes for:

  • Account number
  • Name (first, last)
  • Expiration date
  • PIN number information

For driver's licenses, the magnetic strip contains:

  • Name (first, last, middle)
  • Address
  • State
  • City
  • Postal Code
  • Date of Birth
  • Weight
  • Height
  • Sex
  • Driver's license number / State ID number
  • Hair color
  • Eye color
  • Disability (yes or no, for parking)

Most of the information that is written on the magnetic strip is already written on the card. There are a number of scams that involve the reading of a card's magnetic strip, which is generally called skimming (see Credit Card Scams).

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