Major U.S. banks are rolling out cellphone technology to replace ATM cards that are vulnerable to being lost, stolen or forgotten.

“JPMorgan Chase, which has more A.T.M.s in the United States — 18,000 — than any other bank, has activated this technology on a few hundred machines in four test cities, including Miami and San Francisco,” reports the New York Times. “Six thousand more are already upgraded and ready to go.”

Bank of America and Wells Fargo also have plans to upgrade their automated teller machines to handle phone transactions this year, according to the newspaper.

While the new technology will be more convenient to people who wouldn’t think of leaving the house without a cell phone, it also presents security risks.

“For decades banks have battled “skimming,” in which criminals sabotage ATMs to steal the information off a card and use it to clear out people’s accounts,” according to the NYT. “The replacement of magnetic stripe cards with chip cards significantly reduced that problem, but mobile access brings in new worries.”

A Chase customer was robbed of $2,900 by a thief who got her online user name and password, installed the bank’s mobile app on a cell phone, and used it to withdraw cash. Chase refunded the stolen money and made security changes.

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