Spyware may appear to have died down over the last year or so, but this is not necessarily because it's any less pervasive – rather, spyware writers are getting cleverer in how they design their programs so they're more difficult to detect. 

This is one of the conclusions drawn by McAfee researcher Anna Stepanov, writing in a recent white paper on spyware.
"In the nearly eight years since the first spyware program appeared, the landscape has changed significantly," Stepanova writes. "Spyware has become a business model and a source of significant revenue for cybercriminals.
"At the same time, because of the proliferation of anti-spyware tools, the mechanisms for delivering and executing spyware and other potentially unwanted programs (PUPs) have slowly progressed from the clearly obtrusive pop-up-generating adware to ultra-stealthy espionage tools and Trojan horses.
"In addition, the growing prevalance of rootkits signals a fundamental change in the battle for system security."
She explains that rootkits are a rapidly-growing subset of the PUP market.
"The stealthy nature of rootkits makes their detenction and remediation extremely complex and risky. According to McAfee Avert Labs,m there are more than 12 000 rootkits or variants currently in the wild."
Overall, spyware has moved from merely irritating adware to a technology that has the potential for criminal use, Stepanova writes.
"Spyware has slowly faded from the radar of many home users and IT adminstrators as other technological 'hazards' have taken centre stage in recent months.
"However, the reality of spyware has not changed and, if anything, has morphed in a less perceptible, more egrerious security threat.
"The thrests have changed from the blatantly undesirable pop-up-delivering software to the silently installed piece of tracking software that is imperceptible.
"As the landscape of PUPs and other security threats evolves to meet the fast-paced and changing needs of business and other organisations, we need to be on our guard more than ever.
"We face a stealthy and hidden enemy."