Example , an end user can upload the documents to SharePoint for any approval process taken place, SharePoint administrator can copy or download the Package(.wsp) in the server to deploy it farm wide ,SharePoint designer can download the design template from internet and uploading to SharePoint to create the branding.
In several ways user has to deal with the files, Files are prone to affect by virus or malicious script injection.
By default, SharePoint has feature that allows the user to restrict the certain files types and WebPart configuration security to guard against all malicious intention on the SharePoint server
When user download or opening the malicious file their system or some time their whole network can be affected by virus.
Microsoft also periodically releases the Security Updates for SharePoint 2013.
To defend this problem, SharePoint allows the administrator to set up their antivirus software on all server in the farm.
Here is the detail, I am going to update continuously how the antivirus software works with in SharePoint ecosystem.
To learn more on this, I have the machine with Windows 2008 R2 SP1, SharePoint Server 2013 SP and SQL Server 2008 R2 SP1.
Googling the keyword "Free antivirus for Windows 2008 R2 64bit" and got the "Avast".
This is only for demonstration or learning more about installing the Antivirus on SharePoint not suggesting you or follow the same for your environment.
Download the avast antivirus and doing the custom setup,
Here is the screenshot,
After installing, It shows every thing up to date and all shields are active. Now we test it in SharePoint context.
Now go to your SharePoint Central Administrator Page, click on Security link (_admin/Admin.aspx) from the left hand side , I have modified all the default settings in the page.
After this settings, on my team site, trying to upload the text file and it was little slowness,
and the message was shown to me ,
After rebooting my server , this problem got resolved.