Privacy experts, banks and others are warning consumers about another threat to their personal financial information: electronic "skimming" devices that record credit-card and debit-card numbers at ATMs, gas pumps or vending machines.

Using tiny technology disguised as part of the machine, the thieves then press new cards with customers' numbers and run amok, to the dismay of cardholders such as Kristin R. Kyriakos, 29, of South Baltimore, who returned from vacation Monday to find numerous bank overdraft notices in her mailbox.