Secure Shell

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Contents 1 Secure Shell (SSH) 1.1 Change Port Number 2 Tunneling 3 SCP

Secure Shell (SSH)

Secure Shell (SSH) is a network protocol which transfers data using a secure channel between two networks.

Change Port Number

• Changing the port number for ssh can be one solution to ignore ssh brute force attack.
• Open /etc/ssh/sshd_config file and change the port number.

# Package generated configuration file
# See the sshd(8) manpage for details

# What ports, IPs and protocols we listen for
Port 22

e.g)
Port 1234

• and change the following lines

# Authentication:
LoginGraceTime 120
PermitRootLogin yes
StrictModes yes

to like these lines below

# Authentication:
LoginGraceTime 120
PermitRootLogin no
StrictModes yes
AllowUsers username

Tunneling

-Creating a tunnel through ssh

$ ssh id@<remote machine address> -L <port number on local machine>:<local machine address>:<port on remote machine>

-To forward traffic from port 4881 on the local machine to port 8080 on the remote machine the IP of which is 192.168.0.10.

$ ssh id@192.168.0.10 -L 4881:localhost:8080

-To test a Java web application, running on tomcat server on a remote machine.

$ ssh id@remote.address -L 8080:localhost:8080

-To just forward a port, -N option can be used.

$ ssh id@192.168.0.10 -NL 4881:localhost:8080

-N      Do not execute a remote command.  This is useful for just forwarding ports (protocol version 2 only).

SCP

-Copy a file in the 'dir' directory on the remote machine to the directory 'home' on the local machine.

$ scp -pr username@remote_address:dir/file /home/

-p      Preserves modification times, access times, and modes from the original file.
-r      Recursively copy entire directories.

-Copy a file on the local machine to remote machine

$ scp -p localfile remote.address:dir