Security breaches down under have caused small to medium businesses to fork out more than $600 million last year.

According to a report from the Australian Institute of Criminology, 13 per cent of small businesses, 20 per cent of medium businesses and 30 per cent of large organisations had been affected by a security breach. The survey estimates the cost of security incidents on Australian businesses was between $595 million to $649 million.

Most hacks are virus attacks and with hackers using malicious software such as spyware and keylogging, which captures a user's keystrokes. More than 44 per cent of businesses were hit by malware last year. Phishing attacks were also common with a quarter of Aussie businesses suffering from such attacks.

More than nine per cent of businesses experienced actual theft of hardware such as notebooks and mobile phones, the report said.