We are The Borg - resistance is futile.

Bank security experts are warning consumers who own a bank debit card issued by "Citibank, Bank of America, Wells Fargo, and Washington Mutual, as well as smaller banks" which issue cards to customers to avoid using it at store checkouts.

The list of banks compromised last week by a massive international computer hack appeared in a report by TechNet, which quoted Gartner Research expert Avivah Litan.

Litan added those specific banks are "only the tip of the iceberg" and the damage will continue to spread over the coming weeks.

Law enforcement officials believe thieves broke into the system of a credit card processor interacting with the banks. They first stole the encrypting keys that unscramble the PIN (Personal Identification Number) associated with debit cards.

They then took advantage of lax security at retail chain stores that didn't clear the data from the checkout touch pads where customers input their PIN. This security failure allowed the hackers to combine the debit card number with the associated PIN.

To protect themselves, customers should always press the "Cancel" choice that appears on the touch pad when the sale is completed and the computer asks for the PIN. The store's computer will then process the sale as if the debit card were a credit card and the customer's PIN will not be available for hackers to steal.

In addition, customers should tell their bank or other financial institution to issue a new card to them with a new PIN. Even if the bank or institution they use is not currently listed, it is no guarantee that the institution's PIN files are still safe; it just means that in the 1 week since the hack, there are not yet any public reports of theft in the area. All cards issued using the hacked PIN code - which means all cards issued before the discovery of the hack last week - are vulnerable to theft, and should be replaced with a new card and PIN which will use the new, unhacked, PIN code.

Debit cards are pitched to banking customers as safer than regular checks. They are told that the PIN required to process the card at the checkout means that if the card is lost or stolen, the card can't be used by someone else who doesn't know the PIN.

That advice only applies to a card used at an ATM located at the issuing bank. That is because the transaction is processed directly at the bank, and never goes through a third-party processor.

But that promise of safety is not true if the card is being used at a retail checkout. If the PIN is not punched into the register's touchpad, the card is processed anyway. The card offers no more protection at the checkout than a regular check or credit card.