Fraudulent cash withdrawals have prompted Citibank to re-issue an unspecified number of credit and debit cards. The bank has also blocked PIN-based transactions of Citi-branded MasterCard cards in the UK, Russia and Canada to protect customer accounts. The issue came to light after US Citibank customer Jacob Appelbaum posted on popular blog site Boing Boing details of problems he had with his cards after using a Canadian ATM This fuelled speculation that a widespread ATM fraud issue might be in play.

In response to inquiries by SecurityFocus seeking confirmation of any ATM breach, Citibank has issued the following public statement:

Recently, we became aware of fraudulent ATM cash withdrawls on Citi-branded MasterCard credit and debit cards used in the UK, Russia and Canada on customer accounts that had been possibly compromised in previous retailer breaches in the US. To protect customer accounts that were affected, we placed a special transaction block in those three countries on PIN based transactions. We are currently reissuing cards, as appropriate, to affected customers.

Protecting our customers' accounts and personal information is one of our highest priorities.