McAfee today released the McAfee Threats Report: Fourth Quarter 2011, revealing that malware surpassed the company’s estimate of 75 million unique malware samples last year. Although the release of new malware slowed in Q4, mobile malware continued to increase and recorded its busiest year to date. “The threat landscape continued to evolve in 2011, and we saw a significant shift in motivation for cyber attacks,” said Vincent Weafer, senior vice president of McAfee Labs. “Increasingly, we’ve seen that no organization, platform or device is immune to the increasingly sophisticated and targeted threats. On a global basis, we are conducting more of our personal and business transactions through mobile devices, and this is creating new security risks and challenges in how we safeguard our commercial and personal data.” Malware The overall growth of PC-based malware actually declined throughout Q4 2011, and is significantly lower than Q4 2010. The cumulative number of unique malware samples in the collection still exceeds the 75 million mark. In total, both 2011 and the fourth quarter were by far the busiest periods for mobile malware that McAfee has seen yet, with Android firmly fixed as the largest target for writers of mobile malware. Contributing to the rise in malware were rootkits, or stealth malware. Though rootkits are some of the most sophisticated classifications of malware, designed to evade detection and “live” on a system for a prolonged period, they showed a slight decline in Q4. Fake AV dropped considerably from Q3, while AutoRun and password-stealing Trojan malware show modest declines. In a sharp contrast to Q2 2011, Mac OS malware has remained at very low levels the last two quarters. Web Threats In the third quarter McAfee Labs recorded an average of 6,500 new bad sites per day; this figure shot up to 9,300 sites in Q4. Approximately one in every 400 URLs were malicious on average, and at their highest levels, approximately one in every 200 URLs were malicious. This brings the total of active malicious URLs to more than 700,000.