Usually if we download free software from public file hosting service website, it may contain some virus or keylogger. If you run the program without scanning, it leads to problem in your computer. So it is necessary to scan your files before you run or open.
For scanning purpose, you don’t need any anti virus but Internet.
VirusTotal.com will scan your file and give reports about the file.
if you have the download link, then select submit url and paste url. Click the Send file. It will star the scanning process. Wait for a while.
If you already downloaded the file or want to scan local file, then use upload file.
This virustotal will scan file with all antivirus’ virus signature.