Last month the FBI notified the Thrift Savings Plan, the contribution retirement savings plan for Federal employees, that a contractor's computer systems had been breached in a complex cyber-attack with 123,000 Social Security numbers being compromised.

According to the Federal Retirement Thrift Investment Board (FRTIB) the FBI discovered the breach last month but it was not disclosed until today. The hacking was targeted against computers of Serco Inc., the company that runs the computer systems for the TSP. Initial information indicates that the hacking incident took place in July 2011.

While the company and the FBI don't believe any funds were compromised the intrusion resulted in the theft of the 123,000 social security numbers. Among that group approximately 43,587 individuals had their name, address and Social Security number compromised.

According to the FRTIB, a separate group of 79,614 people had their Social Security numbers and some Thrift Savings Plan information taken.

"In April of 2012, the Federal Bureau of Investigation (FBI) informed the FRTIB and Serco that in July of last year, a computer belonging to Serco, a third party service provider used in support of the TSP, was subjected to an unauthorized access incident. This incident resulted in the unauthorized access to the personal information of 123,201 TSP participants and payees. When the TSP learned of the cyber attack, we took immediate steps to investigate and notify our participants and other affected individuals," the Thrift Savings Plan noted in a news release posted on their website.

The FBI's Cyber Division and The Bureau's Washington Field Office are investigating the breach. The FBI has provided extensive forensic information to Serco and the FRTIB to determine which accounts had been impacted.

"Serco regrets this incident and the inconvenience it may cause to some Thrift Savings Plan participants and payees whose personal data was involved. We have fortified our information security measures and cyber defenses. We are committed to supporting the FRTIB in its mission of providing world-class retirement management solutions for current and former federal employees, members of the uniformed services, and their families," said Ed Casey, Chairman and CEO of Serco Inc.

"We sincerely, regret that this event occurred and will provide assistance and support to the affected individuals through a call center and credit monitoring," said Greg Long, executive director of the FRTIB.

The thrift Savings Plan has posted information and a list of frequently-asked questions on their website to help individuals who may have had their information compromised.