A growing number of illegal online pharmacies are exploiting the web daily, selling dangerous unauthorized prescriptions, according to new report from cyber security experts at Carnegie Mellon University.

Research author Nicolas Christin, associate director of the Information Networking Institute (INI) and colleagues found that rogue websites were redirecting consumers to illicit pharmacies.

By researching the top search result for 218 drug related queries over nine months in 2010-2011, Christian's research team found evidence of substantial manipulation of web search results to promote unauthorized pharmacies.

"We have known for some time that unauthorized online pharmacies have been using email spam to tap the wallets of unwary online consumers, but that method did not blanket enough customers so now the online thieves are infecting websites to redirect unwary consumers to hundreds of illegal online pharmacies,'' Christin says.

Christin and his team reports that one third of the collected search infected websites redirect search results to a few hundred pharmacy websites. Quarter of the top 10 search results actively redirect users to illicit pharmacies, and another 15 percent of the top results were for sites that no longer redirected, but have previously been compromised.

Estimates of the popularity of drug search terms and payment websites help researchers at Carnegie Mellon report that search engine manipulation is considerably more efficient than email spam.

"So, to those who aim to reduce unauthorized pharmaceutical sales, more emphasis needs to be made in combating transactions facilitated by web search,'' said Christin.

The National Association of boards of Pharmacy (NABP) reports that 98 percent of illicit web pharmacy sites continue to operate out of compliance with U.S. pharmacy laws. Also there is a serious danger associated with medicines purchased through fake online pharmacies.