Car rental company Avis has informed around 300,000 of its customers in the US that their personal data has been stolen in a cyberattack.

The company detected unauthorized access to one of its business applications at the beginning of August. “After becoming aware of the incident, we immediately took steps to end the unauthorized access,” Avis told customers in a “Data Breach Notification Letter“ (PDF), a sample of which it registered with the California prosecutor’s office.

It has initiated an investigation in cooperation with security experts and law enforcement authorities, it said.