Bupa's international health insurance arm was hit by a malicious act in its British office, putting the private information of almost 20,000 Australian customers in danger.

The company admitted on Friday that an employee had "inappropriately copied and removed some customer information" at its Bupa Global division, which provides international health insurance for frequent travellers or people who work overseas.

The company admitted on Friday that an employee had "inappropriately copied and removed some customer information" at its Bupa Global division.

"The data taken includes: names, dates of birth, nationalities, and some contact and administrative details including Bupa insurance membership numbers," Bupa Global managing director Sheldon Kenton said.

The data was then "made available to other parties", he added.