"The sites concerned didn't know what was going on. They were small business websites," said Elvira D'Amato, an official at the postal and communications police in Italy, which started the investigation against the spam.
The inquiry is now being coordinated by Europol, the European Union's law enforcement agency, based in The Hague.
Italian police said the investigation began after a grandmother shopping for her grandchildren online in 2009 clicked to a