All posts by Don Matteo

Mark Block and Area in Windows Terminal

in addition to the ability to mark a character, a word and lines, windows terminal also provides to mark a block

A marking mode that can be particularly useful for tabular work. It is allowed to mark and edit information that is directly adjacent to each other, without including the entire lines in the marking and editing.

Mark block and area in Windows Terminal

The Alt key is used for the block marking. Position the mouse pointer at the beginning or end of the block, press the Alt key together with the left mouse button and drag the marker to the other end of the block. The selected block is automatically copied to the clipboard.

Block IP address using Linux Firewall

DDoS and suspicious attacks from source IP addresses can exhaust services and system resources. This tutorial show the commands to block IP addresses on common Linux kernel firewalls

Fire up a terminal and log on to the server by using SSH and then complete the steps for firewalld in the first chapter. The second chapter shows the commands for UFW, and the third shows using iptables.

firewalld commands

firewalld is on RHEL 7 and later, CentOS 7, Fedora 18 and later.

To ensure that firewalld is running on your server, run the following command. If firewalld is not running, go to the iptables chapter.

$ sudo systemctl status firewalld

Run the following command to block the IP address and to add the rule to the permanent set:

$ sudo firewall-cmd --permanent --add-rich-rule="rule family='ipv4' source address='xxx.xxx.xxx.xxx' reject"

Run the following command to reload the firewalld rules:

$ sudo firewall-cmd --reload

Run the following command to list and verify the new rule:

$ sudo firewall-cmd --list-all

Run the following command to remove a blocked IP address.

$ sudo firewall-cmd --remove-rich-rule="rule family='ipv4' source address='xxx.xxx.xxx.xxx' reject"

Run the following command to verify the firewalld is running.

$ firewall-cmd --state

Uncomplicated Firewall (UFW)

ufw is available on Debian 6 and later, Ubuntu 8.04 LTS and later.

To ensure that ufw is running on your server, run the following command. If ufw is not running, go to the iptables chapter.

$ sudo systemctl status ufw

Run the following command to block the IP address:

$ sudo ufw deny from xxx.xxx.xxx.xxx to any

Run the following command to list and verify the new rule:

$ sudo ufw status

Run the following command to remove a blocked IP address.

$ sudo ufw delete 7

Run the following command to show numbered list of firewall rules.

$ ufw status numbered

iptables chains

iptables is commonly pre-installed on all Linux distributions.

Run the following command to block the IP address:

$ sudo iptables -I INPUT -s xxx.xxx.xxx.xxx -j DROP

Run the following command to save the settings. The settings persist after the server reboots.

$ sudo service iptables save

Run the following command to list and verify the new rule:

$ sudo iptables -vnL

Run the following command to delete a iptables chain.

$ sudo iptables -D INPUT 7

Run the following command to show numbered list of iptables chains.

$ sudo iptables -L --line-numbers