It is free and does a good job. I have used it several times.

I like virustotal as a secondary guard against viruses and malware on top of the anti-virus installed on my PC. You can upload files you receive by email or other sources (even large ones) to the site and it scans it with many up-to-date anti-virus applications. The scanning process is fast and you can see if any of the applications found the uploaded file suspicious. You can also scan website URL before clicking them to verify that they are safe. The site user interface is clear and easy to use. Free service.

I like that this software also come with a mobile version you can go and get for your phon. Not only your computer but your mobile device as well can be protexreprotected and scanned.