You are running a web server I assume and although you might be using it locally, you must have either an open port exposing access to it on the public side or your website is a public facing one to being with. In which case, hotlinking to your file is not a virus behavior, its like anyone hotlinking to your resources on the web. There are permissions you can set on your webserver that will prohibit external hotlinking to your files. This will ensure the files are accessible only if they have been delivered through your own webserver/website. To help you fix that, we need to know a few things:
- What web server software are you using? (IIS, Apache, etc.)
- Are you using LOCALHOST/127.0.0.1 like an intranet only or is it public facing accessible? (meaning you either port forwarded 80/88/8080 to your private IP range or if you are using public facing IP and just have the web port open, so typing
http://YOUR_IP brings up your site)
If you are ONLY using it as an intranet and you don't want it to be accessible on the web, then just simply close the web port on your system and it will prevent outside access, simplest solution.
If you want to be able to access it from outside and therefore must have the port open, then you need to use access permissions (or ACL of some kind) to prevent access outside your own website. For this we need to know what web software you are running so specific instructions can be given.
If you are using Apache, then
.htaccess is your best friend and you should really read this and get familiar with this beast. Its a well done resource. You can also look through Apache documentation too. Not as friendly, more technical.
On Windows for IIS, its a bit more complicated but definitely doable, especially they have a GUI for it but you are always welcome to go old school CLI if you like. This lays out a pretty good guide and iis.net is a pretty resource to check as well.
Anything more specific and you have to let us know your configuration, I gave you these links so that if you choose not to and know enough to do it on your own, you have some guides.