Sites liking to 403/DEAD extensions/links. Why ?

Few sites linking to our articles/links from dead URI.

[Future]

Our website URI's are similar to any other website
Our URI's end with .htm or .html or .shtml on various sections

But since last few weeks, we observed a tons of websites liking this URI's negatively.

for links on our website which end up .htm websites (other websites will link same exact pattern to .html which results to 403)

and vice-versa.

Although, we have 403/NOT FOUND pages setup properly, we are not able to understand why we found many new domains coming up with same everyday ?

Thoughts will be helpful, to understand this NEW SPAM MECHANISM, if there !

[caribguy]

You probably mean 404 Not Found, rather than 403 Forbidden :)

I've been seeing hits with filenames in all caps on my server.

This is log spam that attempts two things: create backlinks through publicly accessible log files on the target server, and get the webmaster to visit the site listed in the referrer. The second goal could be a vector for drive-by infections.

Do not visit the spamvertized site. If you want to be brave and take a look make sure that javascript is turned off.

[Future]

Yes I meant 404 not found pages, I found this references from google webmaster tools and not our server logs.