The eCheck Secure service, an electronic payment method provided by the Troy Group, was hacked last month, the company said in a statement.
The Santa Ana, Cal., based-Troy Group also filed a report of the crime with the FBI and has its own analysis firm working on the case, it said.
"Our forensic firm is also advising us on additional preventive measures, and we have implemented their immediate recommendations and are in the process of implementing others," said Patrick J. Dirk, company chairman and chief executive officer, in a statement. "We take information security and the protection of customer records very seriously. We have many safeguards and processes in place. We intend to pursue this criminal action to the fullest and will support the prosecution of this individual or individuals when apprehended."
Scottrade said in an online statement that there is not yet proof that customers' records were used by hackers. The company said it has notified customers of the breach.
"As an update on the situation, there is no evidence that our customers' information was actually accessed or taken from Troy Group. We know than an unauthorized person accessed Troy Group's server but based on the information it received, Scottrade could not determine whether the file with Scottrade's customer information was opened or taken," the statement reads.