(Updates with company comment, more details on illegal access, context on cyber attacks in Australia throughout)

May 10 (Reuters) - Australia's TechnologyOne Ltd said on Wednesday it had detected an unauthorised third-party access to its back-office systems, becoming the latest target in a series of cyber attacks that has bogged companies in the country since last year.

"TechnologyOne's customer-facing SaaS platform is not connected to the Microsoft 365 system, and therefore, has not been impacted," the enterprise software maker reassured its customers in an exchange filing.

The software maker immediately went on a trading halt after the announcement, and said it has isolated the affected systems and will contact the impacted customers after an investigation is conducted.

Starting with the Optus breach last September, a spate of cyber attacks on Australia's corporate sector has exposed data from tens of millions of customers online and led the government to set up a new cyber security body and overhaul rules the home minister has called "bloody useless".

Major firms such as top grocer Woolworths Ltd, and telecoms Telstra and TPG Telecom have reported data breaches and unauthorised access, bringing to light corporate vulnerability to cyber attacks. (Reporting by Sameer Manekar in Bengaluru; Editing by Shinjini Ganguli and Sherry Jacob-Phillips)