The phishing problem at Australian banks has become so problematic it has reached the attention of National Australia Bank CIO who Friday publicly renounced the scams.

The NAB released a statement warning about the risk posed by hoax e-mails designed to "fraudulently obtain consumers' personal information".

The bank's chief information officer Michelle Tredenick said people should be very wary of e-mails purporting to be from their bank, with invitations to click on a link to the bank's Web site.

"These links are usually designed to obtain customers' personal information, including passwords, and may contain viruses that enable fraudsters to track keystrokes," Tredenick said. "Any NAB customer who receives such an e-mail is advised to delete it without clicking on any embedded links."

This follows customer complaints about slow or intermittent Web banking services at the NAB resulting from "a deliberate attempt by external parties to slow or stop NAB's online services".

The phishing attacks effectively resulted in an attack similar to a denial-of-service.

"They did this by jamming NAB's connection to the Internet with hits making it more difficult for legitimate users to gain access," Tredenick said, adding the bank apologizes for any inconvenience and has worked with authorities to resolve the incident.

"Customer information has not been at risk as a result of this issue and our security systems have protected our internal systems," she said. "But the incident highlighted the need for banks and customers to be vigilant at all times."