Hackers have attacked businesses in this Australian city in response to violence against Indian students, a media report said Thursday.

Computers at five Melbourne-based businesses were attacked by a hacker who threatened to attack more companies if the violence continued, ABC Online reported.

A Melbourne construction company says it lost all its data and had to pay $120,000 to repair its computer network, it said.

The report quoted Mark Gregory, a lecturer in Internet security, as saying that it was unusual but not surprising to see cyber hackers motivated by revenge rather than financial gain.

“The motivation here appears to be something that is very topical and in the news at the moment and to suggest that there wouldn't be groups that would use the internet for this type of action would be wrong,” he said.

Gregory told ABC Radio's Jon Faine that it was necessary that organisations do not leave themselves open to such an attack.

“Once people have worked out how to make this type of attack, they can automate it. So they can then attack a large number of companies in a very short space of time,” he added.

“I wouldn't be surprised if this is the tip of the iceberg that you're hearing about,” Gregory said.

There has been a spate of attacks on Indian students in the past nine months in Melbourne and other Australian cities.