It occurred to me today that sic’ing url shortener services on each other to create an infinite loop would be funny. If you aren’t familiar, these are sites that can take a long url (such as http://www.cibomahto.com/2010/04/homebrew-flash-triggers-using-xbee-radios/) and convert it to something shorter (http://bit.ly/bveef4). They have been around for a while, but became really popular for use on Twitter, because the short URLs take up fewer of your precious characters.
At first blush, it seems impossible to do this, since they work by generating a random short URL, however a couple (foolish) services allow you to specify a custom shortlink. So, you can start by using a different service to create a shortlink to a (nonexistent) custom URL on one of those sites, then build a chain by adding new shortlinks that point to the previous link, then seal up the chain by going back and creating the custom URL, pointing it at the last shortlink you created.
The first time I tried this, I only used two links, and Firefox got mad and refused to load the page (smart Fox!). The second time, though, I went for six redirects, and that appears to work. I created this chain:
http://bit.ly/bq66ZB ->
http://w3t.org/GE4 ->
http://urlcut.com/1veuz ->
http://snipurl.com/vi927 ->
http://simurl.com/welkif ->
doiop.com/recurser2 ->
Visiting any of these URLs caused an infinite loop of redirects (until it breaks, because someone fixed their site). A couple things i noticed were:
- The better redirectors blacklist other known redirectors
- Some redirectors actually make you look at an ad before redirecting you (!)
- Some redirectors warn you if they think they are redirecting you to a suspicious url.
My suggestion is to avoid sites sites with such restrictions if you want to do stupid things, or if you run a redirection service, implement all of the above. List of redirectors grabbed from this classy site.
