“This is a security warning, that the file might be harmful or suspicious. It’s crucial to take this warning seriously and avoid downloading the file unless you are absolutely certain it’s safe and from a trusted source. Downloading unknown publisher files off the internet is potentially dangerous. The browser may not be unable to verify the authenticity of the file’s publisher, raising concerns about the file’s origin. When people say its a false positive, make sure you are 100% sure the file is a false positive file. Don’t download any file anyone, unless its a trust source. Don’t disable antivirus program to run files, programs or scripts. Don’t download passworded files and don’t click links from untrust worthy sources. Even friends links can be dangerous if there account has been compromised.”
Go to Don’t Download That File for the description.