The firm said it learned about the attack from federal law enforcement officials who were investigating the theft of data from Scottrade and other financial services firms. News of the attack comes a day after Experian Plc (EXPN.L) disclosed a breach that compromised sensitive data of some 15 million people who sought to open accounts with T-Mobile US Inc (TMUS.N). Scottrade said on its website that its trading platforms and client funds had not been compromised.