C# ‘Hello World’ False Positive

TL;DR

Your C# “Hello World” program is being incorrectly flagged as a virus by your antivirus software. This usually happens because the code looks similar to malicious patterns, or hasn’t been digitally signed. We’ll cover how to report it and temporarily allow it so you can run it, then look at signing your code to prevent this in the future.

Steps

1. Understand Why This Happens
   • Antivirus software uses heuristics – looking for suspicious patterns. Simple C# programs can sometimes trigger these.
   • Lack of a digital signature means your antivirus can’t verify the code’s origin and trustworthiness.
2. Temporarily Allow the Program (Use with Caution!)
   • Find the program in your Antivirus: Open your antivirus software (e.g., Windows Defender, Norton, McAfee). Look for a “Quarantine”, “Threats”, or similar section.
   • Restore/Allow: Your antivirus should list the detected file. There will be an option to restore it (if quarantined) or add an exception/allow it. Be very careful when doing this! Only allow files you created yourself and trust completely.
3. Report the False Positive
   • Find your Antivirus’s Submission Portal: Most antivirus companies have a way to report false positives on their website. Here are some links:
     • Microsoft Defender
     • Norton/Symantec
     • McAfee
   • Submit the File: Upload your C# executable (.exe) to the submission portal and clearly explain it’s a benign “Hello World” program. Provide details about how you created it (e.g., using Visual Studio).
4. Digitally Sign Your Code (Recommended)
   • Get a Code Signing Certificate: You’ll need to purchase a code signing certificate from a trusted Certificate Authority (CA). Some options include DigiCert, Sectigo, and GlobalSign. These cost money.
   • Sign the Executable in Visual Studio:
     1. Open your project properties (right-click on the project in Solution Explorer, select “Properties”).
     2. Go to the “Signing” tab.
     3. Check the “Sign the assembly” box.
     4. Select your code signing certificate from the dropdown menu.
     5. Enter a strong password for the certificate (if required).
     6. Build your project. The executable will now be digitally signed.

   Example Visual Studio Signing Tab settings:

   Sign the assembly: [Checked]
   Certificate: Your Code Signing Certificate
   Timestamp server: http://timestamp.digicert.com

5. Rebuild and Test
   • After signing, rebuild your C# program. The signed executable is much less likely to be flagged as a virus.
   • Test the new executable with your antivirus software to confirm it’s no longer detected.