One thing EE developer forget is that, membership is always set to "ON" in the configuration. Even the membership triggering word is set to "member". This can lead to a lot of spam member registrations, and these members post links in their signatures. In EE, member profiles are public by default. So when you google for your site, these spam links appear in the results as well.
I came across this issue when i was checking AWstats for my website and i saw a lot of spam links in the search keywords. This website illustrates how spammer use inurl method to scan for EE websites
Most of the sites we did didnt use membership at all. What i did to fix these spam links is to
- Turn off membership in the site
- Create a random profile triggering word