At this point, there is no evidence that the compromised data has been misused, although customers are being advised to be on the alert for fraud, Brown said.

Accidental e-mail attachment at Verizon

In a separate incident on Aug. 21, an employee at Verizon Wireless accidentally sent an e-mail with an attachment containing the names, mobile numbers, equipment type and e-mail addresses of nearly 5,000 customers to about 1,800 other Verizon Wireless subscribers. The intended e-mail attachment was supposed to have been an electronic order form.

In an e-mailed comment, a Verizon spokesman said the errant e-mail was "quickly recalled," but he added that some of the recipients had viewed the contents of the file before the recall notice was sent.

The company said it had contacted the 5,000 affected customers and informed them about the breach and advised them of additional "quality control procedures and process improvement" measures that have been implemented to prevent similar lapses in the future.