How outgoing tunnels are not stopped by AV or firewalls?

How can an attacker with initial access to a server behind a firewall, which only has SSH, HTTPS, and HTTP ports open, maintain remote access to the server even after the SSH port is closed by the user on the firewall?

I have searched these questions and answers but none of them directly answering the question:

I knew its by implementing any kind of reverse shell, creating a tunnel that sending outbound connection to attacker server:
Why a tunnel – reverse shell not detected by Firewall or such Antivirus on the OS? until this point, I worked on many computers and tested if a tunnel works or not, none of them blocked me even with enterprise firewall and client security software.

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Which IP address would be most safe and suitable to use as a placeholder in a live system?

Is there a best practice IP address that is safe to use as a placeholder in a live public system on the Internet?
e.g. In a similar capacity, the domain name example.com is reserved and can be safely used without risk of this becoming som… Continue reading Which IP address would be most safe and suitable to use as a placeholder in a live system?

Is it possible to provide Internet to prisoners without risks of them contacting victims or accomplices as a matter of policy?

By securely I mean without the risk of them committing cybercrimes or contacting victims or other people to commit more crimes ? I’ve read that even with firewalls a way around it could be found, especially if the allow list is large enoug… Continue reading Is it possible to provide Internet to prisoners without risks of them contacting victims or accomplices as a matter of policy?

Why does the windows firewall allow apps to communicate through so many different ports and to so many different addresses?

I looked at my default windows defender firewall on Windows 10 22H2, and most of the rules allow apps to communicate through any local port to any remote address and port. I have read other questions and answers but none seem to address th… Continue reading Why does the windows firewall allow apps to communicate through so many different ports and to so many different addresses?