The US-based Symantec, which is best known for its Norton range of PC security software, has agreed to buy web security firm MessageLabs for $695 million. 

Symantec plans to use MessageLabs' technology to develop other online security products. In addition, the company also expects to sell its products to MessageLabs' customers, which are mainly residing outside the US.

MessageLabs produces security products for instant-messaging, e-mail and the internet. The company has regional headquarters in the UK, US and Australia and more than 8 million end users at more than 19,000 businesses. 

MessageLabs is the sixth acquisition announced by Symantec so far this year. However the deal, which is expected to complete by end of this fiscal, is subject to regulatory approval.

Recently, Symantec Corp. has announced the launch of Norton Internet Security 2009 and Norton AntiVirus 2009, in India.