How does an antivirus work?

Question

Antivirus

Good night everybody! I know that there are online services for checking the viruses of any program / file. So, how does this system work, are there any articles on this topic? For some reason, I couldn't find anything similar on the Internet. I found only complete nonsense that does not apply to my question

Thank you for your understanding!

Answer 1

Will the source codes of the best antivirus fit ?
https://github.com/Cisco-Talos/clamav-devel study for health!
Here is the command line documentation for you:
https://linux.die.net/man/1/clamscan
You can check one file, you can check a folder, you can check the entire system.
You can raise the service on nodejs in a couple of hours. The site will be with one upload button, as uploaded, it launches the verification command, and displays the result on the site. Automatic updating of the database file can be started via crontab.
Didn't understand the essence of the question? Do you want to raise the online verification service? Why do you need him?

Answer 2

They don't check anything online. A worker is running on the server that receives the file, parses it, and issues a response. What's under the hood - only service developers know. I can assume that on some sites there may be nothing.