Google is disputing claims Android smartphones have been hijacked and turned into spambots to sell fake Viagra and other pharmaceuticals. Researchers at Microsoft and British-based security firm Sophos reported malware-infected Android phones are sending spam via Yahoo Mail accounts as part of a botnet, but Google and mobile security firm Lookout argue there could be other explanations, CNET.com reported Thursday. \"The evidence does not support the Android botnet claim,\" a Google spokesman said in a statement. \"Our analysis suggests that spammers are using infected computers and a fake mobile signature to try to bypass anti-spam mechanisms in the e-mail platform they\'re using.\" erry Zink, a program manager for Microsoft Forefront Online Security, acknowledged in a blog post the spam could be made to look like it came from Android devices. \"On the other hand,\" he wrote, \"the other possibility is that Android malware has become much more prevalent and because of its ubiquity, there is sufficient motivation for spammers to abuse the platform. The reason these messages appear to come from Android devices is because they did come from Android devices.\" Lookout Chief Technology Officer Kevin Mahaffey said his firm had not confirmed any evidence of a botnet. \"There are a number of alternate explanations that we\'re currently investigating,\" he told CNET.com.