However, Microsoft cautioned that despite the success of the campaign, the computers were still infected with malware despite being cut off. Indeed, Williams claimed that roughly half of the computers “once under the control of Waledac are still trying to send spam – and are in fact doing so at higher levels today than they were in our December analysis”. Microsoft argued this was due to computers being infected with other malware which “may still be directing them [the zombie computers] to conduct attacks outside of Waledac’s control structure”.