Major U.S. banks are detecting unauthorized third-party AI agents operating inside customer accounts, with some agents attempting to take actions that appear to be independent of user instructions, sources tell Axios.

Why it matters: AI agents are becoming a nightmare for America's banks, making their way into banking systems faster than financial institutions can respond.

The difficulty in distinguishing between a human and an unauthorized bot is forcing banks to block the technology and rapidly rewrite their terms of service.

Driving the news : Banks including Morgan Stanley, Bank of America, JPMorgan, Wells Fargo and others are racing to contain agent risks. Some are aware of unauthorized access, people familiar with the issue said.

These are generally situations when an agent or AI assistant accesses a human's account with the user's permission and login credentials.…