The report, on data breaches reported under the Notifiable Data Breach legislation for the second quarter of 2018, did not provide any clues as to the identity of the companies or organisations breached.

It also did not provide a breakdown of breaches for any sector apart from finance and health.

Human resources firm PageUp People, with a list of clients like the Commonwealth Bank. the Australian Broadcasting Corporation, Telstra, NAB, Coles, Aldi, Medibank, Australia Post, Target, Reserve Bank of Australia, Officeworks, Kmart, Linfox, AMP, Asahi, Sony, Newcrest, the University of Tasmania, AMP and Lindt, seems to be the only company that could have leaked the data of a million.

The OAIC said in its report that a total of 242 breaches were reported for the quarter - 65 in April, 87 in May and 90 in June. For the truncated first quarter — since the law took effect on 22 February — the total was 8 in February and 55 in March, 63 in all.

As to individuals affected, the remainder of the breaches did not even come close to the lone million-plus breach; only two breaches affected between 50,000 and 100,000 people and three breaches hit between 10,000 and 25,000.

About 89% of breaches involved contact details, 42% financial details, 39% identity information, 25% health information, 19% leaked tax file numbers, and other unspecified sensitive information was leaked in 8% of cases.

The causes of breaches fell broadly into three categories: human error (36%), malicious or criminal attack (59%), and system faults (5%).

"Attacks included cyber incidents such as phishing, malware, ransomware, brute-force attack, compromised or stolen credentials and hacking by other means, as well as social engineering or impersonation and actions taken by a rogue employee or insider threat," the OAIC said. "Theft of paperwork or storage devices was a significant source of malicious or criminal attacks."

Examples of human error included sending personal information to the wrong recipient by email (22 notifications), mail (10 notifications) or in other ways (eight notifications), and unintended release or publication of personal information (12 notifications).

Among industry sectors, health service providers topped the list (49 breaches reported), followed by finance (36), legal, accounting and management services (20), education (19) and business and professional associations (15). In a footnote, the OAIC said: "State or territory public hospitals and health services are generally not covered – they are bound by state and territory privacy laws, as applicable."

The finance sector includes banks, wealth managers, financial advisers, and superannuation funds, while the education sector includes private education providers who are APP entities and the Australian National University. Other public sector education providers are bound by state and territory privacy laws, as applicable.

The detailed report can be downloaded here.