Thrift Savings Plan account holders remain concerned about potential identity theft following a computer security breach in which personal information on more than 120,000 investors was stolen. But a month after the incident was made public and nearly a year since it occurred, the TSP has seen no sign that the information is being misused, the TSP governing board was told Monday.

The board’s regular meeting fell on the one-month anniversary of the day the TSP publicly announced and sent out letters to affected investors that the computer system of a contractor, Serco, had been hacked in July 2011, with the Social Security numbers of 123,201 investors taken. For about a third of them, names and addresses also were stolen, as was information such as bank routing numbers in some cases. The other two-thirds lost some TSP-related information in addition to their Social Security numbers.

“There has been some anxiety about it, there’s no doubt about it,” TSP Executive Director Greg Long told the board. “Even though there’s some fear about what might happen, to date there’s been no sign at all that data has been misused.”

The TSP is monitoring the affected accounts and has made available the services of a credit monitoring firm. “We and our contractor have taken action relating to this incident and relating to future security,” Long added. “We think we’ve done a very good job in being clear as to what happened.”

Still, he said, the incident has made this “a challenging time for the TSP. We recognize we have a deep well of goodwill and we are drawing from that right now.”

The breach was detected by the FBI, which has refused to comment on how or when it learned of the incident. The TSP and the contractor were notified in early April. Over the weeks leading up to the public announcement, they reviewed data provided by the FBI to determine which investors were affected and what information was lost.

The TSP is a 401(k)-style retirement savings program open to federal employees, uniformed services personnel, and those who keep their accounts open after separating for retirement or other reasons. There are more than 4.5 million account holders.