Holy cow, I wrote a book!
I was in a meeting last year where I learned an interesting tidbit
One of the people at the meeting was looking at the
error reports submitted against Explorer,
and the breakdown went something like this.
For the purpose of discussion, the number of reports have
been normalized into "units", the precise meaning of which is
left unspecified, but is meaningful for comparison purposes.†
The XYZ virus (not its real name) and its variants together are
responsible for the top six categories of Explorer crashes,
and by an enormous margin.
Seventh place, an actual bug, comes in at only 1/80th the rate
of number six; if you group all the XYZ virus failures together,
then the combined virus failures outnumber the most popular Explorer
bug by a factor of nearly 600.
I remember reading a report that half of Explorer crashes can be
directly attributable to malware.
Seeing the top Explorer crash swamped by a single virus
really drives that point home.‡
†I don't know what these units mean either.
‡The anti-malware team is very interested in this data,
because when a new category of Windows crashes suddenly spikes
in popularity, there's a decent chance that a new virus is on