Micro-blogging site Twitter has recently begun filtering tweets containing links to malicious sites.

The tactic was first noticed by security researchers on Monday but has yet to be officially announced by Twitter. It has been designed to prevent surfers from being automatically redirected to sites packed with dangerous exploits.

The widespread use of URL shortening in tweets (which can be no longer than 140 characters) makes it easy to hide the true destination of links in Twitter. The site has thus adopted this approach, following the increased worm, spam, and account-hijacking attacks targeting it.

Whenever a Twitter user attempts to post a link to a known malware/phishing URL, the message “Oops! Your tweet contained a URL to a known malware site!” will appear and, after a few seconds, deletes the tweet.

But the question “Does the feature really work?” remains.

Trend Micro Advanced Threats Researcher Ryan Flores says, “Twitter is filtering malicious sites as a ‘free service’ so we cannot expect it to provide the best protection. After all, this is not Twitter’s core business, micro-blogging is.”

In fact, earlier analysis revealed that the site’s filtering service still cannot block Koobface-related URLs as shown in the figure on the left.

Because it has been a favorite cybercriminal target lately, we cannot blame Twitter for trying but we should not expect too much too soon as well. The effort is a good first step for the site but users should not be complacent just because it is trying to block malicious sites (albeit ineffectively) from being posted as legitimate tweets.

Trust issues are not fundamentally different from other Web, email, and link techniques out there. It all comes down to context and being sufficiently aware of not blindly opening everything others suggest you do.

If you're new here, you may want to subscribe to our RSS feed. Thanks for visiting!