The principal of a Catholic school in WA's Mid West has warned parents their bank details and signatures may have been stolen after the school was targeted in a four-day cyber attack.

Key points: The attack was triggered when someone opened an email, unleashing a virus

The attack was triggered when someone opened an email, unleashing a virus Nagle Catholic College principal Rob Crothers said the attack began last week

Nagle Catholic College principal Rob Crothers said the attack began last week He said other schools had also been targeted and parent bank details potentially compromised

In a letter to parents, Nagle Catholic College principal Rob Crothers expressed his "deep regret" for the data breach, which he said was "highly sophisticated".

He said other schools had also been targeted in the "widespread cyber security attack" that began on June 11.

Mr Crothers told the ABC the cyber attack started after someone mistakenly opened a link in an email sent to the college, which is located in Geraldton about 400 kilometres north of Perth.

"Parents who may have provided information relating to accounts from which to take fee payments or to make payments to the school could have been compromised if they were sent by email format," Mr Crothers said.

"Certainly, anyone who has sent information to the college by email, particularly of a financial nature, would be susceptible to the attack having taken place.

"There's quite a large amount of data. We're still doing discovery on that."

The data breach was reported to Catholic Education WA (CEWA), the umbrella body for Catholic schools in the state.

Mr Crothers said the organisation had hired a security firm and the college was committed to improving cyber security.

"In the long term, what we need to do is look at developing different processes for the handling of this information and provide parents with a different format so they can communicate the same information and not be susceptible through any future email attacks or hacks," he said.

Cyber attack 'shocks' parents

A parent who did not want to be identified said she had cancelled her credit card and ordered another because she was afraid the information may have been stolen.

Another parent, Kyle Pollitt, said the breach was "a shock" but he was satisfied with the school's response.

"I have certainly appreciated that the school has taken the step to notify the parents. I guess it is now up to us and to me as a parent to monitor my own bank accounts," he said.

CEWA issued a statement saying it had been advised "of incidents where employees may have been targeted in an attempted cyber attack".

It said it was not aware of further cyber security incidents in schools or offices that have resulted in confidential information being compromised.

It also said it was working with cyber security experts to "mitigate and address the potential breach".