I believe many people sometimes receive files that are uncertain to contain viruses or unsure about their safety, such as those downloaded from the internet, but you're not sure of their security. Or sometimes, you might feel that there's an issue with your antivirus software and cannot confirm its effectiveness. In such cases, you can use the following method to check the safety of a file in order to protect your computer. I've gathered some online services that provide free virus scanning and check if uploaded files are malicious by using multiple antivirus engines. Recently, I learned about two more: VirusChief and FilterBit. The four most common ones on the web are: VirusTotal (virustotal), Jotti’s Malware Scanner (jotti's malware scanner), VirSCAN (virscan), and Virus.org Malware Scanner (virus.org malware scanner).
I also tested their antivirus effects. If you can't find virus files, you might want to look here: http://bbs3.hypost.cn/thread.php?fid-17.html.
Below are the results of my tests with some virus files. I'm sharing them with you so that in the future, if you come across any suspicious files, you can consider using the websites mentioned below.