American brokerage and banking firm Charles Schwab was hit with a denial of service attack and the company said the problem has been resolved.
The cyber attack shut down the company’s website and mobile applications for about two hours.
Charles Schwab said these attacks did not involve unauthorised access to client accounts or client data.
"We sincerely apologise to each and every one of our valued clients and recognise how frustrating this situation is. We know that uninterrupted access to our websites is a fundamental expectation," the company said.
The company added that a denial-of-service attack is an attempt to disrupt normal access to a website and these attacks are an increasing fact of life in an interconnected world.
Apart from Charles Schwab, several US banks which were affected by disruptions earlier this year include Bank of America, PNC Bank, Wells Fargo, Citigroup, HSBC and SunTrust.
Earlier this year, major US banks sought help from the National Security Agency (NSA) to protect their computer systems following a slew of cyber attacks that disrupted their websites.
A distributed denial of service attack is a cyber exploit where the website is flooded with traffic to shut access to it.
