
I could knit-pick your grammar, but is this overall claim based in empirical research? Linux certainly has it's flaws and while it's not susceptible to WINDOWS malware, it certainly is to a variety of others. Perhaps take a look at http://insecure.org/ or http://www.packetstormsecurity.org/. Both of these sites maintain lists of exploits to various version of Linux and many other types of GNU software as well. Rootkits most generally fall into the realm of 'malware' and once you've got root, baby, you've got the world.
Did Fox News publish this story? Why the hype? `sudo apt-get install gimp*`
Your provider likely runs an rbl check at the smtp server level which is not always the same scanning mechanism - rbl's are continually updated and can be far more accurate at blocking spam if a host or set of hosts are blocked - it can very much seem like a sudden turn around in the amount of email you're getting because known spam sources are eventually blacklisted. So while your isp may not have actually changed anything at their server level the 3rd party rbl filters (spamcop, spamhaus, etc) are continually updating their own lists which directly affect your email.h
Never call a man a fool. Borrow from him.