Free and Open Source blogger with an attitude
This is the quickest way to limit the number of connection to your SSH server with iptables.
[bash]
sudo /sbin/iptables -A INPUT -p tcp –syn –dport 22 -m connlimit –connlimit-above 5 -j REJECT
[/bash]
This will only allow up to 5 concurrent connections to the SSH server, subsequent connections will be rejected by iptables, thus this can thwarts Brute-force attempts to your server.
More Articles About Securing SSH Server
Fail2ban is a security tool used for preventing brute-force attack and Distributed Denial of Service (DDoS) attack to your GNU/Linux box.
Fail2ban monitors failed login attempts and subsequently blocks the ip address from further logins. Although Fail2ban can also be used to secure other services in Ubuntu server, in this post, I will only focus on securing SSH server.
Step 1: Install Fail2ban and (optionally) sendmail
sudo apt-get install fail2ban sudo apt-get install sendmail-bin
Step 2: Setting up Fail2ban
Next, you need to configure fail2ban by creating a copy of ‘jail.conf’ to ‘jail.local’
cd /etc/fail2ban sudo cp jail.conf jail.local
Step 3: General fail2ban configuration
Edit fail2ban configuration file using your favorite text-edito (I personally use ‘nano’)
sudo nano /etc/jail.local
You can set IP address for fail2ban to ignore, IP addresses can be separated by space.
Bantime is the duration of time that you want fail2ban to block suspicious attempt, the value is in seconds
Maxretry is the number of failed attempts before fail2ban block the IP-address, in this case 3600 means 1-hour ban
# "ignoreip" can be an IP address, a CIDR mask or a DNS host ignoreip = 127.0.0.1 192.168.1.1 bantime = 3600 maxretry = 3
Step 4: Enabling ssh and ssh-ddos protection
Find ssh configuration under [ssh] heading, and enable it.
[ssh] enabled = true port = ssh filter = sshd logpath = /var/log/auth.log maxretry = 3
Similarly, you can also enable [ssh-dos] protection by changing the enabled value to “enabled = true”
[ssh-ddos] enabled = true port = ssh filter = sshd-ddos logpath = /var/log/auth.log maxretry = 2
Step 5: Enable Sending Notification Email (optional)
Optionally you can have fail2ban sends you notification email in case of suspicious login detected. To do that, you need to locate destemail settings and changed it to your email
destemail = security@mypapit.net
Fail2ban can use ‘sendmail’ and ‘mail’ application to send notification email
Step 6: (Re-)start Fail2ban
After all is done, you may save the file, and (re)start the fail2ban service
sudo /etc/init.d/fail2ban restart
You can test the configuration by trying to login into your box. You may also check fail2ban log in /var/logs/auth.log (or in other directory specified in jail.local)
For more information about fail2ban, you can read : the official fail2ban manual
Recommended Reading
The video shows how cool Dell Inspiron Duo is when running Ubuntu.
This particular demo uses Ubuntu 10.10 (Maverick Meerkat) with Ubermix customization, which contains a collection of application suitable for netbook users.
Ubermix can be downloaded from its official website, please check the Netbook/table model specific instructions for proper installations.
Supported Netbooks
Netbooks)
sudo is probably the most used command in Ubuntu.
In this post, I will show you how to make ‘sudo’ display funny and humorous error messages in Ubuntu Linux.
To do that, you would only need to edit the /etc/sudoers :
sudo nano /etc/sudoers
Then find the line that starts with Defaults env_reset, add insults at the end of the line so it would look like this:
# See the man page for details on how to write a sudoers file
#
Defaults env_reset, insults
Save the file, and you are done! You can test the results by running the sudo command and entering the wrong password.
Screenshot Demo
Linus Torvalds has announced Linux kernel 3.0-rc1, this marks the end of 2.6.x series line which has 40 releases since late 2003.
To mark this event, Con Kolivas has made a tarball archive (163MB) of all 2.6.x releases available for download. The archive uses lrzip compression which can be installed from the standard Ubuntu apt-get repository.
Note that the size of of the archive after decompression would reach 10.3 GB!
Happy downloading, and hello Linux 3.0!
Apache2 web server will almost always display this information message :
"Could not reliably determine the server's fully qualified name"
when it is first started in Ubuntu and Debian server.
The reason behind this message is because the web server fails to find the suitable domain name in the system.
How to remove the message
First, you need to edit “/etc/hosts” file and put your server name of choice in the file. For example:
127.0.0.1 server.mylocal
Then you need to add “ServerName” directive in the “/etc/apache2/apache2.conf” file.
ServerName server.mylocal
Finally, restart the web server for the changes to take effect. You will notice that the information message is gone now.
$ sudo service apache2 restart