SAN FRANCISCO—Twitter has begun filtering links to known malware sites, the Register reports.

The move was observed by security researchers, though as of Monday, early afternoon, nothing had been officially announced by Twitter.

The ever-growing micro-blogging site seeks to protect its tweeting users from unintentionally visiting sites loaded with malicious software downloads, as well as preventing the infestations of worms, spam as well as stopping account phishing attacks.

Security firms have said URL shortening in Twitter messages—which can be no longer than 140 characters—enables the masking of the the true destination of malware links.

Kaperksy Labs' Costin Raiu noted Twitter appears to be using Google's Safe Browsing API for the process.

"It won't catch everything but is definitely a step forward," he said.