The names, addresses and Social Security numbers of clients of an Arizona dental insurer could have been compromised months ago in a phishing attack, the company said.

Delta Dental of Arizona said that a data breach was discovered in July after suspicious activity originated from an employee’s email account.

Officials at the insurer weren’t certain how many accounts were exposed, but Delta Dental has begun notifying the policyholders.

There have not yet been any reports that personal information has been misused.

The breach is not listed at the Health and Human Services’ Office for Civil Rights, which, by law, must post “breaches of unsecured protected health information affecting 500 or more individuals.”

The breach occurred when an employee opened an email that gave the sender access to the account.

Other information included in the files that could be at risk were usernames and passwords, passport numbers, driver’s license numbers, credit and debit card details and digital signatures.

Delta Dental said it is reviewing its existing security protocols.

Customers who think they have been victimized can call a special toll-free hotline at 1-833-281-4828 Monday through Friday from 7 a.m. until 9 p.m. Arizona time and from 9 a.m. to 6 p.m. Saturday and Sunday.

Click here to learn more about the data breach.