This summer, spammers suddenly happened onto URL shortening services as a prime weapon of choice.
The popularity of URL shortening services has increased in recent years – particularly with the rapid adoption of sites like Twitter, where users have a character limit placed on their messages. There are many different URL shortening sites in operation around the globe. Most allow users to post a long URL into a field and get back a short URL within their domain name. Little in the way of security – such as Captcha puzzles – is built into such sites. This makes them a valuable tool for spammers, as they can introduce e-mail recipients or individuals on peer networking sites to predatory URLs that don't appear malicious.
"The attraction from the spammers is not only is it easy to set up in advance using a number of different services for perhaps the same long URL, that will give a number of different domains that they can then use in their spam messages, and they don't have to break any Captcha in order to do that," said Paul Wood, senior analyst at MessageLabs Intelligence.
MessageLabs started seeing slight spam use of URL shortening services in April. By late June and early July, the company saw three significant spikes in such usage. On July 9, 6.2 percent of all spam was observed using URL shortening services – 9 billion messages in one day alone.
"It's become such a problem for some of these services, particularly…
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