How to prevent application being marked as suspicious

Question

I have a .NET application written in C# using Visual Studio 2012. I'm promoting the application through my own website and have it available for download. When downloading it in Chrome I get a message stating that my application is "not commonly downloaded and could be dangerous". Additionally, when I download my own application and execute it Avast sees it as suspicious and wants to run it in the sandbox.

Is there anyway I can prevent this from happening (without purchasing a certificate for signing)? I don't want potential users to run into this issue.

Edit: I am not doing anything malicious or using any hooks in my application. The application is just a small simple tool as you can see here.

Answer 1

Either you code-sign the App or you wait until a few thousands of people download your App, install it, not report it as garbage and then you get good-will grant from providers.

Answer 2

Even if your application is signed with a certificate issued by one of the CA's participating in Microsoft's Trusted Root Certificate Authority program, it could still face some issues unless you use an EV Authenticode code signing certificate and/or continue to renew the same certificate in perpetuity. See "IE9 SmartScreen Warning, Despite Following All Recommendations" for an example. In short, you're paying for reputation as a software publisher.