The software will be available for
free from Microsoft

From 1700 BST on 29 September, Windows users will be able to download the software from Microsoft's Security Essentials website.

The free software gives basic protection against viruses, trojans, rootkits, and spyware.

The Essentials software is Microsoft's second try at making an own-brand security package.

Prior to release, a beta version of Microsoft's Security Essentials (MSE) software, codenamed Morro, has been available to users in the US, China, Brazil, and Israel.

Genuine PC

Microsoft said the software would be available to anyone who wanted to use it and downloading it would not involve registering with the software firm or having a limit on the amount of time it could be used for.

"It's not being included as part of the operating system or as an automatic update," said Cliff Evans, head of security and privacy at Microsoft UK.

Figures gathered by the Get Safe Online campaign suggest that 50% of PCs in the UK do not have up-to-date anti-malware software installed.

This latest release is intended to help close that gap.

"There are not enough people taking up anti-malware subscriptions," said Mr Evans. "We want to make sure that across the world enough people have access to something."

He said alongside the software, people still needed to run a firewall and keep their browser and operating system up to date with the latest patches and fixes.

The only restriction on use is that it has to be installed on a "genuine" Windows PC - one whose copy of its operating system has been verified by Microsoft.

In the free software market Microsoft faces competition from many others including AVG, Alwil Avast, Avira Antivir and Comodo.

The free software runs on Windows XP, Vista and will also be available for Windows 7 when it is released in late October.

Malware writers

Updates will be provided automatically to those who install the software.

Commenting on Microsoft Security Essentials Roger Thompson, chief research officer for AVG, said: "I do not think it's a bad thing. It's only a bad thing if people think that's all they need to do.

He added: "The danger is if users think that they can just get by with the Microsoft tool."

Mr Thompson alsndered if MSE itself would become a target for malware writers who, if they manage to penetrate it, would potentially have a large pool of victims to target.

Prior trking on Security Essentials, Microsoft offered its Windows Live OneCare paid security software but this failed to win a significant user base in the highly competitive consumer market.

This was retired at the end of June 2009 though Microsoft said it would honour any outstanding subscriptions to the software.