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.

Continue reading How outgoing tunnels are not stopped by AV or firewalls?

Does the traffic tunnelled using Stunnel on port 443:TCP appear the same as normal HTTPS to DPI?

I wrapped my Socks5 traffic in TLS using Stunnel and the Stunnel server is listening on the port 443:tcp.
I can connect successfully to Stunnel server and exchange Socks5 traffic.
From the perspective of DPI (Deep packet inspection), is th… Continue reading Does the traffic tunnelled using Stunnel on port 443:TCP appear the same as normal HTTPS to DPI?

Can I at the same time use Personal VPN on home router/mobile hotspot and company VPN on employers laptop?

I need to travel aborad for few weeks. My company needs my laptop IP from strictely perticular country. I can do that with VPN on router or on my mobile hotspot.
Also for many a times I need to use company VPN for some of my work. I was th… Continue reading Can I at the same time use Personal VPN on home router/mobile hotspot and company VPN on employers laptop?

If a computer gets infected with malware, can the host firewall block the malware from communicating back to its controller on the internet?

I’m trying to figure out how secure a host firewall is, hence the question in the title.
I read that many firewalls allow outbound connections to port 80 to allow browsing, would that be enough for the malware to communicate to the control… Continue reading If a computer gets infected with malware, can the host firewall block the malware from communicating back to its controller on the internet?