Sophos said that underground web affiliate networks called the Partnerka are being used to direct traffic to sites selling versions of the swine flu drug, Tamiflu, which are often counterfeit. Individuals involved with affiliate networks are boasting of earning US$100 000 per day, according to Graham Cluley, senior security specialist at Sophos.

Sophos' Vancouver, Canada-based office released a white paper yesterday entitled The Partnerka – What Is It, And Why Should You Care? It details how the Partnerka work, generating traffic for the online pharmacy websites using a variety of methods.

These include black-hat search engine optimization, in which networks of pages are created using automated text generators in a bid to fool search engines. Many of these pharmaceutical sites, including the ones selling the fake swine flu drug Tamiflu, use the brand 'Canadian Pharmacy' to appear more legitimate.

The sites, which rarely sell the real drug, but instead send non-working and potentially harrmful counterfeit drugs in the mail, are capitalizing on the hysteria over the H1N1 swine flu, Sophos said.

“The criminal gangs working behind the scenes at fake internet pharmacies are putting their customers’ health, personal information and credit card details at risk", Cluley said.

"They have no problem breaking the law to promote these websites, so you can be sure they’ll have no qualms in exploiting your confidential data or selling you medications which may put your life in danger. If you think you need medication go to your real doctor, and stay away from quacks on the internet.”