Fast food restaurant Dairy Queen has confirmed that systems in some of their locations have been infected with malware that puts at risk credit and debit card data of customers of the retail chain.The company has been alerted by the US Secret Service that its systems were affected by a piece of PoS malware also found in hundreds of other retail intrusions.This suggests that Backoff PoS malware is at fault, since this is the threat that has been announced in an advisory from the Department of H…