While the 140-character limitation in Tweets has been heralded as one of the reasons behind the sites success, Symantec has identified that malware authors are capitalising on the popularity of URL-shortening utilities in order to infect Tweeters.

People using Twitter are increasingly opting for URL-shortening tools in order to share links to stories or web sites with their network of followers. These tools take a URL and shorten it, in doing so they also disguise where the link leads.
Until now this has been working well, with Tweeters clicking on links from trusted contacts. However, evidence is mounting that shows malware authors are taking advantage of this trusting relationship.
Ben Nahorney, senior information developer at Symantec, says: “Malware authors are busy distributing misleading applications using these shortened URLs. Using enticing tweets and commonly used twitter search terms, their goal is to get other users to click on their links, leading to malicious code. With the huge amount of fake celebrity accounts, users often do not know who they are interacting with, making clicking on a URL a huge leap of security faith."
Ben Nahorney, senior information developer at Symantec, adds: “Obviously Twitter and the URL shorting services are not at fault here; moreover it is simply another case of malicious attackers using a neutral technology as a means to their deceptive ends. To combat this it is worth noting that both Firefox and Internet Explorer offer browser plug-ins that will check a shortened URL and show the user the final URL before you even click on it. While this won’t say for sure if the link is malicious, it will at least allow the user to look more carefully before clicking."