I guess you could block by IP address or host/domain name, but why bother? Since basically all that is happening is that some other website has a link to your website and they are hiding/shortening the link on their site to your site. I don’t really see any sort of problem with that. For example, this site has well over a 1,000 links to it, which used to actually help a website’s rank (backlinks) in Search Engine ranking, but no longer matters or counts for anything. So since I cannot see a negative or positive impact then what you have is moot/null situation occurring.