29% of Internet users have purchased goods from spam emails, according to Marshal. The most commonly purchased items include sexual enhancement pills, software, adult material and luxury items such as watches, jewellery and clothing. Botnets are networks comprised of thousands of infected personal computers, controlled remotely by criminals. They have enabled spammers to push down their costs through economies of scale and eliminated the need for spammers to host their own spam servers as they simply take control of other people’s computers instead. Recent FBI prosecutions of bot-herders and investigations of message-boards used by spammers, suggests the going rate for spammers to send a mln spam messages is as little as $5-10.