HBO is the latest company in Hollywood to be hit by hackers.

HBO CEO Richard Pepler sent an email to network employees stating that “proprietary information” was stolen in a cyber attack. The network did not disclose, however, which television programs, movies, documentaries, etc was compromised.

The company is working with authorities and cybersecurity firms to investigate the attack.

HBO’s incident is one of several that has plagued Hollywood in the last few years. Netflix’s “Orange is the New Black” was recently hit by hackers who then released 10 episodes of the latest season. Also, in 2014, Sony was victimized in a cyberattack that exposed employee emails and Sony films.