Lincoln National Corp. (LNC) last week disclosed a security vulnerability in its portfolio information system that could have compromised the account data of approximately 1.2 million customers.

In a disclosure letter (PDF) sent to the attorney general of New Hampshire Jan. 4, attorneys for the financial services firm revealed that a breach of the Lincoln portfolio information system had been reported to the Financial Industry Regulatory Authority (FINRA) by an unidentified source last August. The company was planning to issue notification to the affected customers on Jan. 6, the letter says.

The letter does not give technical details about the breach, but it indicates the unidentified source sent FINRA a username and password to the portfolio management system.

"This username and password had been shared among certain employees of [Lincoln Financial Services] and employees of affiliated companies," the letter says. "The sharing of usernames and passwords is not permitted under the LNC security policy."

FINRA declined to tell Lincoln whether the source of the username and password was a current employee or some other party, according to the letter.

Upon further investigation, Lincoln found another of its subsidiaries, Lincoln Financial Advisers, was using shared usernames and passwords to access the portfolio information management system, the letter states. In the end the company found a total of six shared usernames and passwords, which were created as early as 2002.

The passwords were "created and distributed by the system administration team to certain home office and support staff to perform administrative functions, respond to registered representative inquiries and review client account activity," the letter says.

The forensic team that investigated the breach found no evidence that the data had been used outside of the company, either by hackers or former employers, according to the letter. The portfolio management system consolidates data about customer accounts -- and therefore contains a good deal of personal information -- but it doesn't allow the user to actually access those accounts, the letter says.

Lincoln says it has "discontinued" all shared usernames and passwords in its systems, and it is notifiying customers, offering them identity theft services.

Have a comment on this story? Please click "Discuss" below. If you'd like to contact Dark Reading's editors directly, send us a message.