Well, I have been software developer since 14 years and used to install and configure windows based networks, and others before Windows exists... Avast is a software made to protect your PC from viruses, trojans, etc. It has nothing to do with this spam on this forum.
I use AVAST since many months for my personal use at home. It is a great product, and it is free !
Many other "famous" sites were affected by spam. MS, HP and others, were hacked before, and also banks, and even NASA. There will always be a danger on Internet because it is basically "opened" to all.