Butler County has started the process of notifying people affected by an October data breach, according to an update on its website.

According to the notice, on Oct. 2, federal law enforcement alerted the county to suspicious activity involving its computer network.

“Upon being notified, the county immediately began working with a nationally recognized digital forensics team to secure its network and investigate the scope of the incident,” said the notice.

On Oct. 30, the county determined that there had been unauthorized access to, and acquisition of, personally identifiable information maintained on the county’s network. Subsequent investigation focused on finding what data was involved and who was affected.

On Jan. 22, the county completed the review and began locating mailing addresses for individuals whose information may have been impacted, so that it could provide them with written notice of this incident.

According to the statement on the county website, the county has notified local and federal law enforcement and continues to cooperate with federal law enforcement’s investigation into this incident.

“Please be assured that the county continues to closely monitor its systems, data, and network access,” the notice said. “Additionally, the county is continuing to evaluate and make changes to strengthen its network against any future incidents.”

The county is advising those affected to take appropriate steps to protect their personal information, including reviewing and monitoring any account statements, free credit reports and health insurance explanation of benefits forms for unauthorized or suspicious activity.

If an individual’s Social Security number, driver’s license number and/or state identification card number was involved, the county will offer credit monitoring services at no cost.