The Australian Red Cross (ARC), which has about 60 staff distributing grants of up to $20,000 per application, has come under attack by computer-generated applications for bushfire relief assistance.

ARC's director of Australian Services Noel Clement said they are weeding out false claims but it's time consuming and wastes resources.

"There have been hundreds of automated attempts to access financial assistance," he told AAP.

"There are a couple of hundred claims that we have concerns about and we are working through all of those and we have already referred a number of cases to the police.

He said in one community alone we had applications for 15 homes that had been destroyed but when they physically checked the addresses none of them had been impacted by the fires.

An Australian Charities and Not-for-profits Commission representative said online fraud was a constant challenge for charities that drained limited resources and forced them to engage cybersecurity experts.

"This can be time-consuming, expensive and resource intensive."

A spokeswoman for the National Bushfire Recovery Agency said they are working closely with the Commonwealth Fraud Prevention Centre to build robust fraud prevention strategies into computer programs.

She also warned of an SMS scam that offered increased tax relief for donations.

Australian Associated Press