URL shorteners, like bit.ly, moby.to and tinyurl.com, do three things:
- Make a URL shorter
- Track clicks on the URL
- Hide the destination URL
Making URLs shorter was their original role, and it’s why they’re so common in media where the raw URL is visible to the recipient – instant messaging, twitter and other microblogs, and in plain text email where the “real” URL won’t fit on a single line.
From the moment they were invented they’ve been used to trick people to click on links to pages they’d rather not visit, from musical classics to less tasteful content. And, in just the same way, spammers quickly found that they were a good way to avoid content-based filters or to hide a suspicious looking target URL.
Inevitably, URL shorteners that are persistently abused by spammers (especially those where that’s done with the support of the URL shortener operator) start to be seen as a sign of spam, and email that uses them will be treated with suspicion by content-based spam filters and often sent to the spam folder.
bit.ly is probably the highest profile URL shortener, so it’s the one you’ll most likely see people trying to use in email. What effects does that have?
Now being “totally owned” by the Canadian Pharmacy gang, thousands of URLs being spammed with very slow takedowns. Not good.SpamHaus on bit.ly
bit.ly have been on SpamHaus’s radar for quite a while. They’re listed on the SBL multiple times. They’re listed in the DBL – SpamHaus’s newish domain based blacklist, intended for content-based filtering of email. All this means that emails that contain bit.ly URLs are increasingly likely to have serious delivery problems.
This isn’t unique to bit.ly: many other URL shorteners have similar problems – j.mp, su.pr, and others. Nor is it unique to SpamHaus: many other spam filters, public and private, are starting to treat common URL shorteners with suspicion.
Naive use of URL shorteners in your email will send it to the spam folder.