Marriott International faces a fine for a data breach that came about after the company acquired Starwood Hotels & Resorts Worldwide Hotels in September 2016. The breach affected the data for more than 300 million guests.

THE UNITED KINGDOM’S Information Commissioner’s Office plans to fine Marriott International £99,200,396, or just over $123 million, in connection with a massive breach of the company’s guest reservation database last year. Marriott President and CEO Arne Sorenson said the company is disappointed in the ICO’s decision and it will fight to defend its position.

Marriott announced the breach in November, saying when it acquired Starwood Hotels & Resorts Worldwide Hotels in September 2016 the old reservation system was compromised. That led to a data breach that compromised the information of more than 300 million guests.

The ICO said it found that Marriott failed to undertake sufficient due diligence when it made the Starwood acquisition.

“Organizations must be accountable for the personal data they hold. This can include carrying out proper due diligence when making a corporate acquisition, and putting in place proper accountability measures to assess not only what personal data has been acquired, but also how it is protected,” Information Commissioner Elizabeth Denham said in a statement. “Personal data has a real value so organizations have a legal duty to ensure its security, just like they would do with any other asset.”

Sorenson took issue with the ICO’s position in his own statement Thursday.

Marriott President and CEO Arne Sorenson testified before the U.S. Homeland Security & Government Affairs Permanent Subcommittee in March on the company’s efforts to prevent future leaks.

“We are disappointed with this notice of intent from the ICO, which we will contest. Marriott has been cooperating with the ICO throughout its investigation into the incident, which involved a criminal attack against the Starwood guest reservation database,” Sorenson said. “We deeply regret this incident happened.”

Sorenson appeared before the U.S. Homeland Security & Government Affairs Permanent Subcommittee in March to report on Marriott’s efforts to secure its systems since the breach.

“We are focused on identity access management, which means a broader deployment of two-factor authentication across our systems, as well as network segmentation, which means isolating the most valuable data so that it becomes more difficult for attackers to access the systems and for malware to spread through the environment,” Sorenson said in that testimony. “We know that this is a race that has no finish line. Cyber-attacks are a pervasive threat.”

The ICO said it will consider Marriott’s arguments in its defense before making a final decision on the fine.