I have some small experience in this area. @AwesomeOpossum74
has it right, although his post may be too technical for some people.
Simply put, I would not attach a Windows 7 or earlier system to the internet.
If you have one, upgrade it to Windows 10, replace it, or get it off the internet by the end of this month (January 2020). DO NOT rely on anti-virus programs, a firewall, or your router to keep you safe.
When Microsoft releases a security fix for Windows 10 and other supported versions of Windows, hackers analyze it to learn what vulnerability it fixes, and then race to develop an exploit. They scan the internet for vulnerable systems, and hack websites to spread their malware when you visit, too. You may not know it, but your internet connection is being probed constantly.
-> Historically, approximately 1/3 of reported vulnerabilities also apply to older systems like Windows 7. Those older systems will never receive the fixes, leaving them open to attack.
-> Historically, most people with infected systems do not know that their systems are infected. You are not the exception.
I cannot make it plainer than that.