URL shorteners are so common these days people don’t give them a second thought. Especially on social media sites like Facebook and Twitter. Some common URL shorteners are
The list is endless. You can even make your own service, which is exactly what spammers are now doing.
Spam messages are now being posted on Twitter with these new URL shorteners and it’s difficult to filter them out. E.g. URLs that begin with
The best thing you can do is to use a modern web browser that does some URL scanning, such as Chrome, Opera, or IE9 (older versions of IE are vulnerable). Also buy and install a good virus scanner.
More information about URL shorteners here.