Charles Schwab Corp said it was the target of a cyber attack that prevented access to its website intermittently for about an hour on Wednesday, the second such attack in as many days, but that the problem had been resolved.
Schwab, one of the largest U.S. brokerages, said on Tuesday afternoon it was that target of a distributed denial of service attack - an attack that floods websites with traffic in order to block access - that left clients unable to trade through the site for two hours.
Phone service was available during both attacks, although responses were slower than usual due to the large number of people calling in, said Schwab spokesman Greg Gable.
He said clients who believe they were affected by the outage can call 1-800-435-4000 to talk with a Schwab representative.
The attacks did not impact client data or accounts, Gable added.
Schwab said it is actively investigating the attacks but could not provide further information.
The San Francisco-based company had 8.9 million active brokerage accounts and $2.1 trillion in total client assets at the end of the last quarter.