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On 30 April 2015 the three independent security testing bodies AV-Comparatives, AV-TEST and Virus Bulletin published a joint press release criticizing Qihoo 360 after they found that Qihoo 360 had submitted products for comparative which behaved significantly different from end user products. The products for comparative used an engine by Bitdefender, while the end user products use Qihoo 360's own QVM engine instead. The testing bodies claimed that the end user products would provide a considerably lower level of protection and a higher likelihood of false positives. As a consequence the three testing bodies revoked all certifications and rankings from earlier that year.
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Qihoo 360 denied cheating allegations claiming that the QVM engine developed by Qihoo 360 would be more effective in China.
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