Landry’s Inc., the parent company of more than 600 restaurants, hotels and casinos, has announced a data breach exposing customers’ card payment information.

Company officials reported a hacker accessed and installed malware to their network supporting payment processing, which is used by servers to swipe and charge customer credit cards. They said encryption technology made the card data unreadable on some payment-processing devices, however other devices used by staff might have exposed card payment data. Personal information put at risk includes cardholder names, card numbers, expiration dates and verification codes.

The breach took place between March and October. The number of affected customers hasn’t been disclosed.

Company leaders advised customers to monitor their credit information for suspicious activity.

“It is always advisable for individuals to closely monitor their payment card statements for any unauthorized activity,” officials said in a statement on the company website. “Customers should immediately report any unauthorized charges to the financial institution that issued the card because payment card rules generally provide that cardholders are not responsible for unauthorized charges reported in a timely manner.”

Based out of Houston, Landry’s operates more than 60 restaurant chains and more than 600 restaurants, including Joe’s Crab Shack, Charley’s Crab, Claim Jumper and Rainforest Café, along with hotel and casino chains such as the Golden Nugget in Las Vegas and Atlantic City.