VeriSign, Websense and Sophos will all be helping Bit.ly to ensure that as little malware and spam as possible makes it through its URL shortening service.

VeriSign's iDefense IP reputation service uses a blacklist of URLs, domains, and IP addresses serving up malicious content to analyze incoming URLs and block unwanted destinations.

Websense will be providing its Threatseeker Cloud, which analyzes web content using heuristic tools and reputation data.

Finally. Sophos will be providing behavioral analysis technology to look for spam and malware.

"Sophos is an innovative security service whose behavioral-analysis technology goes beyond blacklists, to proactively detect spam and malware", said Bit.ly on its blog.

This is part of a general move on Bit.ly's part to use multiple independent providers when scanning the URLs that it shortens. The defense in depth idea, in which it uses different scanning engines and techniques, is the best way to stop as many malicious URLs as possible. The service also allows users to add a '+' sign to the end of shortened Bit.ly URLs if they want to preview the destination behind a URL before opening it.

The Twitter micro-blogging site uses Bit.ly as its official URL shortening service.

The announcement will come as something of a slap in the face for Kaspersky, which recently announced Krab Krawler, an internal project that scans the URLs being served up by Bit.ly and tries to ensure that they are secure.