The SANS Institute has revealed that hundreds of emails from an internal account were forwarded to an unknown third party, compromising 28,000 records of personally identifiable information (PII).

The global cybersecurity training and certifications organization said in a statement that the incident came to light on August 6 after a regular review of email configuration identified a “suspicious forwarding rule.”

“This rule was found to have forwarded a number of emails from a specific individual’s e-mail account to an unknown external email address,” it continued.

“The forwarded emails included files that contained some subset of email, first name, last name, work title, company name, industry, address, and country of residence. SANS quickly stopped any further release of information from the account.”

SANS Institute confirmed to Infosecurity that the exposed data belonged to individuals that had registered for one of its virtual summits and “was intended for community outreach purposes.” That means no customer or instructor records were compromised.

In total, 513 emails were forwarded to the external address, exposing nearly 30,000 records of PII. A malicious Office 365 add-on was apparently installed on the victim’s machine as part of the attack.

“We have identified a single phishing e-mail as the vector of the attack,” SANS explained. “As a result of the e-mail, a single employee’s email account was impacted. Aside from the affected user, we currently believe that no other accounts or systems at SANS were compromised.”

The firm said its digital forensics team is currently investigating whether any other information was compromised, and to identify any opportunities to build resilience into its defenses and improvements into its incident response for the future.

No passwords or financial information was taken in the attack, and all affected individuals have now been notified, SANS said.

Refreshingly, the organization added that it may run an online session on the incident once the investigation is completed, “if there is information that we think would be useful to the community.”