What is GPG? GPG (GNU Privacy Guard) is a free and open-source tool that implements the OpenPGP standard for encrypting and signing data. It’s commonly used to: GPG uses asymmetric encryption â meaning it relies on two keys: đ ď¸ Installing GPG Check if GPG is already installed: gpg –version If not, install it: đ Step … Continue reading đ Getting Started with GPG: Encrypt and Decrypt Files Using GPG Keys
Compiling source code produces a binary. During compilation, you can provide flags to the compiler to enable or disable certain properties on the binary. Some of these properties are relevant to security. Checksec is a nifty little tool (and shell script) that, among other functions, identifies the security properties that were built into a binary … Continue reading Identify security properties on Linux using checksec
Cron is one of Linuxâs most useful tools and a developer favorite because it allows you to run automated commands at specific periods, dates, and intervals using both general-purpose and task-specific scripts. Given that description, you can imagine how system admins use it to automate backup tasks, directory cleaning, notifications, etc. Cron jobs run in … Continue reading Create and Manage Cron Jobs on Linux
Using an outgoing SMTP server is the traditional method of sending emails. An alternative solution is to bypass the SMTP server and send it directly to the destination. Itâs known as Direct Send, and you can use it through specific email software programs. Direct Send is not very reliable though, and here is why: It … Continue reading Set Up SMTP Server
A DMZ, or demilitarized zone, is used to help improve the security of an organizationâs network by segregating devices, such as computers and servers, on the opposite sides of a firewall. And setting up a DMZ in your home router designates a device as a DMZ host and will forward all the ports to that … Continue reading What is a DMZ?
Minifying JavaScript files can reduce payload sizes and script parse time. The Opportunities section of your Lighthouse report lists all un-minified JavaScript files, along with the potential savings in kibibytes (KiB) when these files are minified. How to minify your JavaScript files Minification is the process of removing whitespace and any code that is not … Continue reading Minify JavaScript
This is useful for putting rules on the input chain. Usually, you will have a DROP rule at the end of the chain, so if you want to add a new rule, it should go before DROP. To start, figure out which line should be used for the new rule. iptables -L -n –line-numbers You … Continue reading iptables insert rule at a specific position (prepend)
Quick post today showing some different ways to block visitors via their IP address. This can be useful for a variety of reasons, including stopping some stupid script kiddie from harassing your site or preventing some creepy stalker loser from lurking around your forums or even silencing the endless supply of angry trolls that never seem to … Continue reading How to Block IP Address with .htaccess
PING â ping is a computer network administration software utility used to test the reachability of a host on an Internet Protocol network. It is available for virtually all operating systems that have networking capability, including most embedded network administration software. Blocking PING on the server is helpful sometimes, if the server continues to face any type of DDoS … Continue reading Managing PING through iptables
IPv4 has been in use since the start of the Internet and is widely deployed across the Internet, and home networks. In this tutorial, we will cover the basics of IPv4 Addresses. You will Learn IPv4 address structure IPV4 Address classes Special and reserved IP addresses Broadcast Basics Note: If you are new to binary numbers then … Continue reading IPv4 Explained for Beginners
IPV6 has been developed to replace IPV4 which is running out of addresses. Although it has been around almost 10 years it is still not widely deployed and supported. However, adoption rates are increasing rapidly and IPv6 traffic crossed the 10% threshold in February 2016 (wiki). For small business/home and home office networks, it is likely to … Continue reading IPv6 Explained for Beginners
Big-endian and little-endian are two formats to store multibyte data types into a computer’s memory. These two formats are also called network byte order and host byte order respectively. In a multibyte data type such as int or long or any other multibyte data type the right most byte is called the least significant byte and the left most byte is called the most significant byte. … Continue reading Checking whether the underlying architecture is little-endian or big-endian using C
Setuid Program Example Hereâs an example showing how to set up a program that changes its effective user ID. This is part of a game program called caber-toss that manipulates file scores that should be writable only by the game program itself. The program assumes that its executable file will be installed with the setuid bit set and … Continue reading How to switch from root user to non-root user during execution using C on Linux
If you search the web you can find a number of references to programs/scripts that convert diff output to HTML. This is a bash version. The script expects “unified” diff output (diff -u) on its standard input and produces a self-contained colorized HTML page on its standard output. Consider the two files: #include <stdio.h> // main main() { printf(“Hello … Continue reading Convert diff output to colorized HTML
An archive file is nothing but a collection of files and directories stored in one file. Please note that by default the archive file is not compressed. A compressed file uses less disk space. This blog page explains how to compress, list, and extract files using the tar command on Linux or Unix-like systems. Compress … Continue reading How to compress files with tar command on Linux/Unix
Using PHP Itâs really simple to convert a DateTime from one time zone to another in PHP. Just create a DateTime object using date & time to be converted as the first parameter and the original time zone as the second parameter. Then change the time zone to the desired one using the setTimezone method. Thatâs all! $date = new DateTime(‘2022-02-01 … Continue reading How to Convert Date and Time from One Time Zone to Another
1. 10 Minute Mail Maybe you want to sign up for a site which requires that you provide an e-mail address to send validation e-mail to. And maybe you don’t want to give up your real e-mail address and end up on a bunch of spam lists. This is nice and disposable. 2. Flightradar24 Flightradar24 … Continue reading 5 Amazing Websites on the Internet
Sockets provide the communication mechanism between two computers using TCP. A client program creates a socket on its end of the communication and attempts to connect that socket to a server. When the connection is made, the server creates a socket object at the end of the communication. The client and the server can now … Continue reading Java Socket Programming – Send the file using TCP Sockets
Sockets provide the communication mechanism between two computers using TCP. A client program creates a socket on its end of the communication and attempts to connect that socket to a server. When the connection is made, the server creates a socket object at the end of the communication. The client and the server can now … Continue reading C Socket Programming – Send the file using TCP Sockets
#ifndef COMPLEX_H #define COMPLEX_H #include <iostream> #include <fstream> #include <string> #include <complex> class Complex { private: double real; double imag; public: Complex(); Complex(const Complex& obj); Complex(const std::string& str); Complex(double real); Complex(double real, double imag); double real_num() const; double imag_num() const; std::string toString() const; Complex operator+(const Complex& rhs) const; Complex operator-(const Complex& rhs) const; Complex operator*(const … Continue reading Handling complex number using C++ class
A program written in c language to solve a 2Ă3, 3Ă2, 3Ă3 sliding block puzzle. 1. DFS (Brute-Force)We can perform depth-first search on state space (Set of all configurations of a given problem i.e. all states that can be reached from initial state) tree. Image source: https://courses.cs.washington.edu In this solution, successive moves can take us away … Continue reading Sliding Block Puzzle Solver(2Ă3, 3Ă2, 3Ă3) â C++ Programming