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SSH Security: How To Block SSH Brute Force Attacks with SSHGuard

SSHGuard monitors logging activity and reacts to attacks by blocking their source IP addresses. sshguard has born for protecting SSH servers from the today's widespread brute force attacks, and evolved to an extensible log supervisor for blocking attacks to applications in real-time.

SSHGuard is given log messages in its standard input. By means of a parser, it decides whether an entry is normal activity or attack. After a number of attacks, the IP address is blocked with the firewall.

These are the available blocking backends:

  • SSHGuard with PF (OpenBSD, FreeBSD, NetBSD, DragonFly BSD)
  • SSHGuard with IP FILTER (FreeBSD, NetBSD, Solaris)
  • SSHGuard with IPFW (FreeBSD, Mac OS X)
  • SSHGuard with netfilter/iptables (Linux)
  • SSHGuard with TCP wrappers / hosts.allow (almost any UNIX system)
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SSH Security Tips – OpenSSH hardening security

In this article I'll show you some tricks to help you securing your OpenSSH service. Here you will find useful information on how to secure sshd and prevent ssh dictionary attack.

1. SSH security by tweaking sshd_config

The OpenSSH server configuration file is located in /etc/ssh/sshd_config. You need to restart sshd after every change you make to that file in order for changes to take effect.

  • Change port number

Moving the SSH daemon off of port 22 protects you against automated attacks which assume that sshd is running on port 22.

Port 34912

  • Allow only SSH protocol 2

Only SSH protocol version 2 connections should be permitted. Version 1 of the protocol contains security vulnerabilities. The default setting shipped in the configuration file is correct, but it's important to check.

Protocol 2

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How To Set Up OpenSSH Public Key Authentication

Secure Shell or SSH is a network protocol that allows data to be exchanged using a secure channel between two networked devices. Used primarily on GNU/Linux and Unix based systems to access shell accounts, SSH was designed as a replacement for Telnet and other insecure remote shells.

Before we start, make sure your computer has a SSH client installed and the remote Linux system has SSH installed and sshd running.

1. Generating RSA key

You will need to generate the local RSA key by running the following command:

# ssh-keygen -t rsa

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