Temporary employment agency Randstad was the target of hackers, the company announced on Thursday.
The hackers entered the company's servers and had access to data about Randstad's activities in the United States, Poland, Italy and France.
Randstad recently discovered the hack and engaged cyber security experts and forensic investigators.
This investigation is currently ongoing.
It is not known whether Dutch data has also been captured.
The investigation revealed that a hacker group called Egregor was behind the cyber attack.
That group has now published some of the stolen data.
It is not yet clear what the size of the data breach is.
Despite the hack, Randstad was able to continue working. The company has reported the hack to regulators and investigative services.