JPMorgan Chase & Co. Chief Executive Officer Jamie Dimon said the biggest U.S. bank will probably double its $250 million annual computer-security budget within the next five years.

Dimon, whose company recently disclosed that an attack by hackers exposed contact information of 76 million households and 7 million small businesses, made the remarks today at an event sponsored by the Institute of International Finance in Washington.

"It's about firewall protection, it's about internal protection, it's about vendor protection, it's about everything that hooks up into you," Dimon, 58, said in his first public appearance since beginning treatment for throat cancer. "There will be a lot of battles. Unfortunately some will be lost."

JPMorgan last week outlined details of the scope of the breach, first reported in August, saying there was no evidence that customer account numbers and passwords were compromised. Banks work with each other to help fend off hackers, and a "legal safe harbor" could be needed to foster more cooperation, Dimon said today.

Dimon disclosed July 1 that he would begin eight weeks of radiation and chemotherapy to treat the disease, and said his prognosis was excellent. The CEO has been working at the New York-based bank while being treated, and made Lee Raymond, JPMorgan's lead director, available if managers needed guidance while he was away.

Dimon, who appeared thinner than before his cancer treatments, was joined at the event by fellow CEOs James Gorman of Morgan Stanley and Brian T. Moynihan of Bank of America Corp., as well as Deutsche Bank AG Co-CEO Anshu Jain.

JPMorgan is scheduled to report third-quarter results on Oct. 14.