How did it happen?
The Abta website was caught up in a cyber attack, it said this may have affected 43,000 people.
Files which were accessed may well have included personal information of anyone who had made a complaint to an Abta registered travel agent.
The hack occurred on the 27 February, Abta is currently making contact with any of those it believes may have been affected. It also has a dedicated help line.
The firm has also told the police and the Information Commissioner’s Office (ICO) of the incident.
As part of the ICOs role it must help the public manage their personal data.
Abta chief executive Mark Tanzer has said he would “personally like to apologise for the anxiety and concern”.
“It is extremely disappointing that our web server, managed for Abta through a third party web developer and hosting company, was compromised and we are taking every step we can to help those affected.”