F-secure counted 250,000 new malware samples over the year 2007, which is the same amount that was counted over the last 20 years (including 2006). These statistics are very different from vendor to vendor, since most of them are based on the particular vendor's clients' experiences.
Having said that, many other security vendors have reported a great increase in malware as well, Symantec, for example estimated the increase at 185%, a similar number.
According to Mikko Hypponen of F-secure, hackers “are generating large number of different malware variants on purpose to make the lives of antivirus vendors more difficult.”
These “variants” are simply malware that appears to be different but actually belongs to one or another malware “tree” and uses the same code and has the same functions. Many of them use tactics such as “jumbling up” the code in order to obfuscate the nature or the program and encryptions.
F-secure said that quality has been changed by quantity, when it comes to malware. This means that security vendors will have to try harder than ever to keep the cyber-criminals at bay.