A site being “spamvertized” means that the site is being included as a link in spam emails. The most common reason your site appears in spam emails when you’re not the spammer is because your site has been hacked by someone.
The hacker places a small piece of code somewhere on your site that redirects a user to a different site. They do this because including their own website in emails they send will immediately flag spam detectors. Their site is already a known-bad-site. So they’d rather spamvertize your site to try and get more emails through spam filters.
This works for a while until your website is also associated with spam and they have to move on to another “clean” website that they can spamvertize and that will redirect to their own site.
Once the hacker has sent out enough spam that includes a link to your site (which redirects to their site), your website becomes associated with spam (and blocked by spam filters). This is about the time you find out that your site is being “spamvertized” because your host will receive complaints about emails that include links to your site.
This is one of the main reasons today why sites are hacked – because spammers need new “clean” sites to spamvertize and redirect to their own sites.
