The information you send to the bank is encrypted so that only the bank can identify what you are sending. Anyone else who is viewing your activity over the Internet would only see the equivalent of a jumble of letters and numbers. The technology used is called SSL or Secure Sockets Layer. It secures and authenticates the user through a secure browser. This provides 128 bit encryption and is widely accepted as standard for processing financial transactions.
Banks protect the servers that hold the information and programs needed to operate an online bank.
One of the measures they take to do this is deploying firewalls. Firewalls are a combination of computer hardware and software that restrict the flow of information between computers. In some cases, firewalls permit information to flow in only one direction, so that hackers can't enter, and only authorized information can flow out. Finally, we have another page that list the many additional and specific steps banks take to protect your security. If you are interested in more information we encourage you to visit this page.