Ticker Talk:

National Discount Brokers Group said a 70-minute outage on its Web site Thursday was caused by hackers in an attack similar to those experienced by other sites earlier this month. The brokerage’s site was slow in the early morning and shut down at about 10 a.m. PST, according to Dennis Marino, chairman of NDB.com. “It has all the earmarks of the denial-of-service” attack, Marino said. In such attacks--much like those launched against Yahoo Inc., E-Trade Group Inc. and others earlier this month--Web sites are overloaded with frivolous inquiries from other computers. No customer account information was jeopardized in the attack, Marino said. NDB stock rose $3 to close at $35 on the New York Stock Exchange.