This is an informative post. I see you updated it with more background.
Did you uninstall TeamViewer? I'd scan your computer for malware and perhaps another security program (MalwareBytes) just for an overkill.
Did you delete the TeamViewer executable from your computer?
Also, review your firewall settings for any mysterious-looking open ports. This may be difficult because all allowed programs look mysterious but you could always remove the rule and then re-allow after using the applicable, known, trusted program.
Look into your Windows Explorer (or equivalent) for any unknown programs configured to launch during boot and login.
