Exposing your software to the internet resulting in initial access via:

1. Vulnerabilities being exploited (either 0 day or unpatched)

2. Credential stuffing or brute forcing credentials

Then depending on the vulnerability or account compromised, access to your home network where they can move laterally and install ransomware, serve spam emails or links, or mine bit coin. These are the most common scenarios.

Best practice is to not expose ports for this reason.

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