Thinking aloud here. How common are actual computer viruses (not just malware / ransomware, etc) these days? Meaning, an unauthorized program running on a co

Thinking aloud here. How common are actual computer viruses (not just malware / ransomware, etc) these days? Meaning, an unauthorized program running on a computer that attempts to propagate itself to other computers. This was a real problem in the past when a program would be written to exploit shoddy network code, or when we still used removable media more frequently. I think all the modern OS vendors have locked their platforms down to prevent this mode of attack.