Secure Shell, also known as SSH, is an Application layer protocol. It uses a secure channel to ensure that data is exchanged between two IP devices. A Cisco IPv6 router may act as either an ssh client or server. A Cisco IPv6 router can act as an SSH server or client. CSF is the best way to block user logins and monitor them. CSF is a free Intrusion Detection System that can be used on all VPS systems. It also includes an iptables-based firewall application. Once you have installed CSF make sure to remove port 22 from your incoming TCP_PORT options and add your new chosen SSH port to the list. Edit the /etc/csf/csf.conf and restart the CSF service by running /etc/init.d/csf.
This is the easiest precaution to take, but it does help reduce unauthorized login attempts to your VPS through the SSH service. The default SSH port 22 is used. Every security scan against a VPS will check to see if it is open. Let’s close the port by moving it well out of the way. This is the best way to secure your SSH service. It will stop users from accessing your UK VPS using password-based authentication. Instead, each user must authenticate by first providing a key and then entering corresponding passwords. The authentication process is now more secure because you need both the key and password to log in. First, we will need to create a local key pairing on an Open SSH client system. In this example, we will use a Linux computer. When asked for the passphrase, enter your login password. This is what you will need to enter when connecting to your VPS: # SSL-keygen Generating public/private RSA key pair
Before the introduction of SSH to Cisco IOS the only remote login protocol was Telnet. Telnet, although functional, is not secure. The entire session, including authentication, is in clear text and is therefore subject to snooping. SSH is both an application and a protocol that replaces Telnet. It provides remote administration of Cisco network devices such as routers, switches, security appliances, and security appliances. Cisco IOS contains both an SSH client and an SSHserver. This document focuses on the configuration of the SSHserver component. You must have an IPSec (3DES or DES) encryption software from Cisco IOS Release 12.1(1)T installed on your router. The IPSec component is included in advanced IP services images. This document was written using c2800nm-advipservicesk9-mz.123-14.T5.bin. Your router must be configured with a hostname as well as a domain name.