On Wednesday, MGM Resorts said that all of its casinos and hotels were “operating normally” following a system shutdown of some of its computer systems, following some cyber security issues it experienced earlier in the month.

With over 30 hotels and casinos it operates around the world, including in Las Vegas and Macau, Reuters reported that the company was targeted by a hacking group named Scattered Spider, according to two sources with knowledge of the matter.

On its website, MGM reported, “Mobile Check-In and Digital Keys are currently unavailable.” 

Over the past year, several security analysts have called attention to Scattered Spider, noting in particular its sophisticated social engineering tactics. It has been documented to target the information security systems of a target company by using a phone call, in which it will pretend to be an employee who needs their password reset.

The hacking group reported last week that it had stolen six terabytes of data in hacks of the computer systems of multi-billion-dollar casino operators MGM Resorts, and Caesars Entertainment. Both companies stated they were investigating the hacks.

In a note last week, brokerage Jeffries stated, “Indications from MGM confirming the cyberattacks should be taken as one-time, largely insurable events that should not have long-lasting impacts on the businesses.”