More than 33,000 Mainers were affected by a data breach of the education software provider PowerSchool last month, according to a notification the company filed Monday with the Office of the Maine Attorney General.

The global K-12 software company suffered a cybersecurity breach that occurred on Dec. 19 and was discovered on Dec. 28, according to the notification. The company says 33,488 Maine residents were affected, although it does not include details about which school districts were impacted. There are about 170,000 publicly enrolled students in Maine, according to the state Department of Education.

At least nine Maine districts, including Brunswick, Cumberland, Gardiner and Yarmouth, notified families of the breach in email notifications or online announcements this month.

Monday’s filing includes a template of a letter from PowerSchool that districts could use to notify affected families. It includes a summary of the breach situation, which it describes as an “unauthorized exfiltration of certain personal information from PowerSchool Student Information System (SIS) environments through one of our community-focused customer support portals, PowerSource.”

The letter also explains what personal information might have been accessed.

“Due to differences in customer requirements, the types of information involved in this incident included one or more of the following, which varied by person: name, contact information, date of birth, Social Security number, limited medical alert information, and other related information,” the letter states.

It also offers options for affected individuals to enroll in complimentary credit monitoring or identity protection for two years.

Brian Gagnon, chief technology officer at Portland-based IT firm Uprise Partners, said signing up for credit and identity monitoring services can minimize the risk of data being used for fraudulent purposes, but little can be done to reverse leaks of personal information.

“Once the data is out of the barn it’s a lot harder to do something,” Gagnon said.

Individuals have little control over what services organizations like a school department use to manage personal data, which can make it difficult to take preventive action, Gagnon said.

“This is a collective problem. It’s not an individual problem,” he said. “We as consumers need to hold people accountable with our data. Our data has a lot of value. It also has a lot of expense to us users when it’s not treated well.”