They are turning to infiltrating legitimate websites on which to host their attacks -- a technique known as "hack-and-pier," according to Finnish anti-virus firm F-Secure.
Normally, internet service providers take down fraudulent websites within 24 hours, according to research, but when an authentic site is the culprit, much more work is involved.
"The site cannot simply be pulled offline without collateral damage to the legitimate business," Sean Sullivan, a technical specialist at F-Secure, said Wednesday on the company's blog. "So the website's administrator must be contacted to repair the damage."
Sullivan mentioned B.B.C. Sales & Service, a Canada-based beverage equipment provider, as one of a number of legitimate websites that has been exploited to host phishing scams. A company spokeswoman did not immediately respond to a request for comment Wednesday.
Sullivan said that until websites repair vulnerabilities that permit hackers access, this new style of attack will continue.