When you’re only given 140 characters to share your message with the world, abbreviations become very, very useful.

The use of shortened URLs that point to pages whose original URLs are of ungodly lengths is probably the most common form of abbreviation on Twitter, where 140 characters is the rule. For example, posting http://vator.tv/n/9ba instead of the full http://vator.tv/news/show/2009-08-03-ads-become-focus-for-yahoo-in-microsoft-deal saved me about 60 characters on my last tweet, which I used to describe my post and to add words that might help users find the tweet in searches.

The only problem with these URLs is that, while the original poster may know where the link leads, nobody else has any idea. Although my example of a shortened URL above clearly points to a page on Vator.tv, the most popular URL shorteners, like bit.ly, are completely ambiguous in the links they provide. One link, http://bit.ly/oVF1q, points to Facebook and another, http://bit.ly/17MgN8, points to Twitter.

But the shortened URLs indicate no difference in their addresses about their destinations. For all we know, any random user’s Twitter post may claim to link to an article about tech breaking news, even if the link actually posts to a site with malware or some malicious scripts running in the background.

Because of this vulnerability, in tandem with the network’s exploding popularity, the site has increasingly become a target for worms and spam attacks.

Well, Twitter is finally doing something about it, according to multiple users and news sources.

Now, when a user attempts to post a malicious shortened link, Twitter warns you, “Oops! Your tweet contained a URL to a known malware site!” On third-party clients, posts with bad links are outright blocked without any explanation.

All of us on Twitter certainly welcome this upgrade, despite the lateness in its implementation. Users can be more confident now searching the site and clicking random links to their hearts’ content.

Twitter has not yet officially announced this update.