Cyber Alarm Antivirus for Salesforce provides a native Force.com prevention capability to scan Attachments before they can enter into your Salesforce platform. Cyber Alarm maintains a comprehensive list of Antivirus Signatures which are updated daily.
To activate all of the features of Cyber Alarm including real time upload protection, you can email firstname.lastname@example.org to request a quotation for a full license.
Utilizing the free version you can use Cyber Alarm Antivirus against a selection of previously uploaded attachments. You can also download the Eicar.com AV Test File to test the virus scanner detection capability here: http://www.eicar.org/85-0-Download.html