Malware was on roll during the first quarter of this year as the number of machines infected by botnets hit the 5 million mark worldwide, and PC malware at its highest level in four years.

Mobile malware, too, was on a tear, according to new McAfee data for the first quarter of 2012, with 8,000 new mobile malware samples found, 7,000 of which were for the Android. That's more than a 1,200 percent increase over the fourth quarter of 2011, according to McAfee.

The Cutwail botnet recruited the most bots during that period, with more than 2 million new infections. Bots were on the rise in Columbia, Japan, Poland, Spain, and the U.S., and McAfee says it costs criminals about $2,399 for the Zeus variant Citadel, plus $125 to rent a botnet builder and administration package. It costs another $395 for automatic updates for AV-evading tools.

Distributed denial-of-service (DDoS) botnets are cheaper, ranging from $450 to $1,000, depending on the features.

McAfee collected 83 million pieces of malware in Q1, up from 75 million in Q4. Why the big jump? More rootkits and password-stealers were among the samples discovered. There were 250 new Mac malware samples in Q1, but malware targeting the Apple platform is on the rise, according to the report.

"Malicious code is on the rise again. Plain and simple. We are seeing more malware than in the recent past and you can count on that figure to rise in the coming year," said Dave Marcus, director of security research for McAfee Labs, in a blog post. "In particular, mobile platforms present today’s cybercriminal with an almost irresistible target, specifically Android-based for now, but that can certainly evolve."

Spam dropped worldwide to around 1 trillion spam messages per month as of the end of March, according to the McAfee report, which is available here for download (PDF).

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