Linux Internals (17)

Introduction to SUID

The level of access that users and system processes have to files in Linux is governed by file permissions, attributes, and ownership. This is done to make sure that only legitimate users and programs are able to access particular files and directories.

Environment Variables in Linux

While working with Linux systems to run scripts or applications, you may encounter an error like this: ‘environment variable not set.’ Environment variables are an important feature of Linux systems (you will also find it on Windows and OSX). This blog post will introduce you to what environment variables are, how they can be created on Linux systems and their significance in cybersecurity.

Vi Editor in Linux

Whenever you use a Linux system, you will encounter text files and configuration files that you will need to edit. There are a variety of text editors across all Linux distributions to help you for this task. Most, text editor applications come with a GUI. On Linux server machines and other specific distros, only a command-line version of the operating system is available. In that case, a non-GUI based text editor must be used. This blog post introduces you to the command-line based Vi text editor, that is installed on most Linux systems by default.

Installing Software on Linux Distributions With Package Managers

When using Linux systems on a regular basis, you may need to install additional software applications. This task can be done using package managers. Depending on the type of Linux distribution, different package managers can be used. This blog post introduces you to the various packages managers available across Linux distributions.

So many Linux commands and switches – How do I remember them all?

As a cybersecurity professional, you will encounter and use Linux systems quite often. Most of the time, you will be using the Terminal application to run some commands on your system. There is a long list of commands that can be used on the terminal and each command has numerous switches. It is intimidating to have to remember them all. This blog post tells you how you can work your way around Linux commands and their switches.

Don't be tricked by hidden files: Viewing hidden files and directories in Linux

Did you know that it is possible to hide files and directories on a Linux system? This is actually a legitimate feature that exists by default, that has been misused by cyber adversaries. This blog post will introduce you to the ‘hiding’ feature present on Linux systems and present its security implications.

Creating and Executing Linux Shell Scripts

Previously we discussed the concept of Linux shell scripts. In this article we are going to write our first script, take a look at how to execute it, plus discuss the importance of shebang and function of chmod command.

Linux Resource Monitoring Commands

As security professionals, we must continually take a look at how processes, individuals, or items utilize system resources. This blog post will present you with fundamental Linux commands that you may use in your everyday security duties.

Linux Shell Scripts: Automate Your Command Line Tasks

Have you tried using powerful Linux commands to view the contents of a file, perform basic file and directory operations or even to view the permissions assigned to a file? Assume there is a scenario where you are required to run a particular set of commands, many times. It will be nice to have a solution that can run multiple commands in one go, without having to type out the commands repeatedly. One solution is to use shell scripts. Or say you want to perform some tasks based on the results of one command – scripts come in handy then. This blog posts introduces you to the power of shell scripts in Linux systems.

Managing Linux User Accounts

In a previous article we discussed Linux Account Types. In this blog article, we will discuss managing Linux user accounts.

Root Login vs. Sudo

This blog will explain why you should quit logging in as root at all times and provide the best security alternative to doing so.

File Types in Linux

Think about a library. It has a lot of books – there would be children’s books, magazines, graphic novels, encyclopedias, mystery novels, etc. But they are all books. Here book is a blanket term for every type of it. On a Linux computer, every single file or directory that you see is referred to by the blanket term file. This means that a directory is also a type of file. Interesting, right? There are more types of files that a Linux system works with. This blog post introduces you to the different types of files on a Linux system.

File Permissions in Linux

Every file on a Linux system has a name, its data and associated metadata. The metadata includes the timestamps associated with the file (creation time, modification time, access time), user that the file belongs to, group that the file belongs to, security information for the file, etc. The security information for a file includes the permissions assigned to it. The permissions will dictate which user or group will have access to the file and also define the level of access. This blog post introduces you to how permissions exist for a file in Linux.

User Accounts on Linux Systems

It is important to have a mechanism to manage the various users on a computer and the access they can have to the data on the computer. On Windows machines, you may have encountered administrators and regular users whose activity on the system is controlled by administrators. This means a Windows machine would have an administrator account and user accounts. In the same way, on Linux machines too there is a mechanism to manage the various types of user accounts. This blog post will introduce you to the various types of user accounts on Linux and their significance for cybersecurity.

Linux Command Line 101: Basic Redirection and Pipes

When using the Linux command line, you may need to save the output of a command to a file. In some cases, you may need process the output of one command using another one. In these situations some special command-line operators prove to be useful. This blog post gives you a brief introduction to how redirection and pipe operators can be used in the Linux command line.

Linux Command Line 101: Viewing File Contents

Most files on Linux are flat files storing text data, comma-separated values (CSV), tab-separated values (TSV), configuration information, etc. In some situations, you may need to view and process the contents of files. Although it can be done using text editor applications, there are some powerful command-line tools that can be used over the terminal. This blog post discusses some of the basic commands used to process the contents of a file.

Linux Command Line 101: Basic File and Directory Operations

The ability to use the Linux terminal is a valuable skill for a cybersecurity professional. Many tasks in cybersecurity domains like penetration testing, digital forensics, cloud security involve using Linux commands on a regular basis. Knowing how to use simple commands will help you easily interpret and use complex commands. This blog post introduces you to some basic commands to manage files and directories. The following operations were performed on Ubuntu. The commands discussed in this blog post would be the same across all Linux distributions.