The personal information of more than 769,000 retired state employees and other beneficiaries has been stolen in the US state of California, authorities said Thursday.

The California Public Employees' Retirement System said in a statement that a third-party vendor, which utilized the MOVEit file transfer program for the purpose of informing them about member deaths and verifying payment eligibility, experienced a security breach.

The hackers stole data on the members' names, dates of birth, social security numbers and the names of family members.

The criminal group responsible for the cyberattack, identified as Cl0p, is engaging in extortion by threatening to release victims' data online unless they comply with their demands for payment, according to ABC News.

The cyberattack against MOVEit was reportedly carried out by Russian hackers. (Anadolu Agency)

•PHOTO:The criminal gang behind the hack, known as Cl0p, is extorting victims, threatening to dump their data online if they don’t pay up. GETTY IMAGES/ISTOCKPHOTO