TPG Telecom joined a growing lists of companies in Australia to be hit by data breaches, with the operator disclosing a hosted exchange storing information for up to 15,000 business customers was compromised.

In a stock market filing, TPG Telecom explained it was informed by its external cybersecurity adviser Mandiant of unauthorised access to an exchange service which hosts email accounts for iiNet and Westnet internet and mobile subscribers on 13 December.

TPG Telecom stated it took steps to stop the breach of the Microsoft-hosted exchange service, with a preliminary review finding the main aim of the hack was to search for customers’ cryptocurrency and financial information.

The operator added it is investigating and will inform customers of any potential impact. It added home and personal iiNet and Westnet services were not impacted.

An attack on rival Optus in September resulted in unauthorised access of current and former customers’ information.

A month later, Singtel’s local IT services consulting company Dialog Group’s servers were compromised in an attack involving access of some client and employee information.