Banks are struggling with cybersecurity. That doesn’t bode well for other industries.

Banks are supposed to be among the most secure places on earth, guarded against physical attacks and cyber intrusions by extensive security measures. But after JPMorgan Chase, the country's largest bank, said this week that more than 80 million customers were affected by a breach of its computer system, security experts warn that Wall Street remains vulnerable to cyberattacks and other industries may be even worse off. The JPMorgan attack affected significantly more people than many expe...