The volume of malware samples detected by McAfee passed the 75 million milestone late last year, the Intel-owned security firm reported this week.

Although the release of new malware slowed in Q4 2011, mobile malware continued to increase albeit from a low base. Android was by far the most targeted platform with 400 new strains appearing in just that quarter, compared to a cumulative total of little over 100 prior to the last three months of 2011. For comparison, there were four million new strains of Windows malware in Q4 2011, compared to 6m in Q2 2011.

Scareware volumes dropped considerably between Q3 and Q4 2011, while AutoRun and password-stealing Trojan malware each showed modest declines over the same period. Mac-specific malware, which spiked in Q2 2011, dropped off in the last two quarters of last year. In June 2011, more than 250 new samples were detected but this figure trailed off to less than 50 in Q4 2011. Almost all the June samples were designed to power fake anti-virus for Mac scams.

McAfee advises Mac fans to not discount security threats, despite the decline.

"Mac malware had a big spike in the second quarter but has remained quiet since then. As always, comparing overall malware growth for the Mac with that for PCs makes the Mac threat look rather tame, but it’s always wise to protect your system, even if it’s a MacBook Air."

McAfee Labs recorded an average of 9,300 new bad websites per day in Q4, up from 6,500 in the previous quarter. The vast majority of new malicious sites were hosted in the US, followed by the Netherlands, Canada, South Korea and Germany.

While the malware outlook remains bleak there was much better news on the junk mail front. Global spam reached its lowest point in years at the end of last year, according to McAfee. Somewhere around 1 trillion spam messages were dispatched per day in December 2011, compared to 2 trillion in May 2011. The volume of legitimate email hovered at between 450 and 500 billion messages a day during 2011. Although that put spam volumes at more than 70 per cent the figure is much improved from the dark days of the Naughties when spam volumes routinely exceeded 90 per cent.

McAfee doesn't comment on the reasons for the decline but other observers credit the dismantling of various pharma spam operations and botnet takedowns for lower volumes of junk mail.

Instead of merely coping with the sheer volumes of junk email hitting servers, the latest challenge is countering targeted attacks. "Despite the drop in global levels, spear-phishing and spam are as dangerous as ever," McAfee concludes. McAfee’s third-quarter threat report can be found here [PDF]. ®