Bit.ly, the popular URL shortening service, has signed a number of deals aimed at improving the security of its redirects.

The site can reduce long web addresses (URLs) down to just a few characters, which makes it very popular on micro-blogging site Twitter as well as other social network sites such as Facebook.

Bit.ly has partnered with Websense, Sophos and VeriSign to protect users against spam and malware threats.

Websense will be deploying its ThreatSeeker Cloud service to analyse and categorise content behind shortened links. The security firm says that it will examine a host of factors such as the URL, property type, lexical and search reputation, history, age, geography and neighbouring properties to determine if a site is safe or not. If the site is a known malicious, spam or phishing site it will block the user from accessing it.

Bit.ly will be using malicious behaviour analysis and detection platforms from Sophos to dynamically identify new malware.

Finally, the service will be using VeriSign’s iDefense IP reputation service to detect malware through its blacklist, which includes “URLs, domains, and IP addresses which host exploits, malicious code, command and control servers, drop sites and other nefarious activity,” bit.ly said on its blog.

The service shortened over two billion links in October this year alone, according to Websense.