Google has said that a massive breach, which may have begun three months ago, led to the theft of a significant amount of customer data.

Google, a subsidiary of Alphabet, said in a post that the hacking group suspected of carrying out the attacks, CL0P, has a long record of targeting third-party software and service providers.

“This level of investment suggests the threat actor(s) responsible for the initial intrusion likely dedicated significant resources to pre-attack research,” the company said, according to Reuters.

The tech giant, which operates a major cybersecurity arm alongside its well-known search, email, and video services, noted that the attackers targeted Oracle’s E-Business Suite, a set of applications used by Oracle customers to manage operations such as customer relations, supply chains, manufacturing, and logistics.

In a separate statement, Google analyst Austin Larsen said, “We are aware of dozens of victims, but we expect there are many more. Based on the scale of previous CL0P campaigns, it is likely there are over a hundred.”

Oracle did not immediately respond to an email request for comment.