The state of malware today
At the end of 2001, approximately 60,000 forms of malware or threats were known to exist. This number was a significant increase from 1996 (about 10,000) and 1991 (about 1,000).
Approximate growth of malware since 1991
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Over the last decade, the proliferation of malware has become an online crime story. Today, estimates of the number of known computer threats such as viruses, worms, trojans, exploits, backdoors, password stealers, spyware, and other variations of potentially unwanted software range into the millions.
Ever since criminal malware developers began using client and server polymorphism (the ability for malware to dynamically create different forms of itself to thwart antimalware programs), it has become increasingly difficult to answer the question “How many threat variants are there?” Polymorphism means that there can be as many threat variants as infected computers can produce; that is, the number is only limited by malware’s ability to generate new variations of itself.
It has become less meaningful to count the number of threat variants than it is to detect and eliminate their sources. In 2011, more than 49,000 different unique threat families were reported to the MMPC from customers. Many of these reported families were duplicates, polymorphic versions of key threat families; detecting and eliminating key threat families from infected computers is an ongoing activity.
In 2011 Microsoft added more than 22,000 signatures to detect key threat families. As criminal malware developers create more threats, the size of typical antimalware signature files increases; today antimalware signature files range to more than 100 MB in size. In 2002, typical antimalware signature files were less than 1 MB in size.
