TD Ameritrade Holding Corp. said Friday one of its databases was hacked and contact information for more than 6.3 million customers was stolen.
A spokeswoman for the Omaha-based brokerage firm said more sensitive information in the same database, including Social Security numbers and account data, does not appear to have been taken.
The company would not share many details of its investigation, including when the hack took place, because it is still looking into the theft and is cooperating with investigators from the FBI.
Ameritrade's customers have received unwanted e-mail ads because of the data theft. Spokeswoman Katrina Becker said there is no evidence that any customer suffered financial losses or was a victim of identity theft.
Ameritrade (up $0.14 to $17.98, Charts) plans to notify its customers about the data theft Friday, and the brokerage firm posted information on its Web site.
"While the financial assets our clients hold with us were never touched, and there is no evidence that our clients' Social Security numbers were taken, we understand that this issue has increased unwanted SPAM, which is annoying and inconvenient for them," Chief Executive Joe Moglia said in a statement.
"We sincerely apologize for that and any added concern this may have caused."
Ameritrade said it is confident that it identified how this information was taken and has changed its computer code enough to prevent the theft from recurring. It added that any new client who opened an account after July 18 was not affected.