The fundamentals of persistence with Bash

Persistence refers to maintaining access to a compromised system after the initial exploitation. For pentesters assessing Linux systems, understanding Bash-based persistence techniques is essential. This section covers some fundamental methods for establishing persistence using Bash.

Creating a new user in Bash

One basic technique is to create a new user account with root privileges. See the following example for the commands to add a new user with root privileges:

$ sudo useradd -m -s /bin/bash bashdoor
$ sudo usermod -aG sudo bashdoor
$ echo "bashdoor:password123" | sudo chpasswd

These commands create a new user named bashdoor, add them to the sudo group, and set their password to password123. The new user will have full root access.

Let’s take a closer look at how this works:

• useradd: Creates the new user account
• -m: Creates a home directory
• -s: Sets the login shell to bash
• usermod -aG:...