Large-scale data breaches affecting thousands of customers at a time jumped 33 per cent in the first six months of the year, before a string of high-profile cyberattacks that revealed sensitive information about millions of Australians, new data reveals.

While the Optus and Medibank data breaches have shone a spotlight on cybersecurity in the past two months, fresh data from the Office of the Australian Information Commissioner covering the first half of 2022 revealed it had been alerted to 396 breaches involving companies with revenue of more than $3 million.