Malware's on the march, according to a security technology company, with the most recent three-month period seeing the biggest increase in four years in the number of examples of software behaving badly. And having a non-Windows operating system (OS) or mobile device is no longer an insurance policy: "As PC malware writers master their craft, they continue to transfer their skills to other popular consumer and business platforms, such as Google's Android OS," the company reported.

Since the first quarter of this year, researchers at McAfee say they have detected an increase of 1.5 million malware samples and have identified new approaches such as mobile "drive-by downloads," the use of Twitter for control of mobile botnets, and the appearance of mobile "ransomware." McAfee, which provides computer security software, published the findings of 500 multidisciplinary researchers in 30 countries in its quarterly Threats Report.

Ransomware, which restricts access to a computer's system or files, has become a popular avenue for cybercriminals, steadily increasing quarter over quarter, McAfee said. Havoc can range from loss of a home user's photos and personal files to demands for money from large enterprises. Ransomware is especially problematic, as it can hold computers and data hostage, instantly damaging machines.

Botnets, a network of compromised computers infected with malicious software and used to generate spam, send viruses or cause Web servers to fail, have also taken center stage again this quarter with infections reaching a 12-month high, the survey showed. With the U.S. as the global hub of botnet control servers, new methods for control have been uncovered, including the use of Twitter for mobile botnet command and control, enabling attackers to tweet commands with relative anonymity.

McAfee researchers also saw a migration of drive-by downloads from the desktop to mobile devices. Drive-by downloads take place without user knowledge, usually when an infected site is visited.

"Over the last quarter we have seen prime examples of malware that impacted consumers, businesses, and critical infrastructure facilities," said Vincent Weafer, senior vice president of McAfee Labs. "Attacks that we’ve traditionally seen on PCs are now making their way to other devices. For example, in Q2 we saw Flashback, which targeted Macintosh devices, and techniques such as ransomware and drive-by downloads targeting mobile. This report highlights the need for protection on all devices that may be used to access the Internet."

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