Email filtering company Mailguard is warning about an active phishing campaign emanating from compromised email accounts hosted on Optus' optusnet.com.au domain.
The messages purport to be advice recipients of remittance advices, invoices and insurance documents that are available for download.
Should users click on the links to the documents in the messages, they will download malware.
While Mailguard said the emails originate from a large number of compromised addresses using the optusnet.com.au domain, a company representative declined to reveal to iTnews how many had been detected.
Optus has been contacted for comment on the phishing attack which appears to have started around the 8th of this month.