Commerce Bank, which is a regional bank in US, said that it was the victim of a security breach but the attack was quickly stopped and the law enforcement was notified.
Commerce Bank, which operates banks in five U.S. states, said Tuesday that a hacker gained access to a database with about 3,000 customer records and accessed data belonging to 20 of them. The bank is contacting those who may have been affected.
Those customers will also be getting two years of free credit monitoring in case their numbers were stolen.
Bank officials say they did manage to stop the hacker, using a top secret system with several levels of security that is supposed to protect the information of all 1.5 million customers.
The hacker however was able to access information from at least 20 customers.
It wasn't clear how the hacker accessed the bank's database. A common method is by passing malicious data through Web-based forms, known as a SQL injection, which can force the database to reveal other information it holds.
Hackers often look for vulnerabilities in bank and e-commerce Web sites that will allow them to tap into their back-end databases.
