Here are some sensitive files in Linux that attackers might seek to exploit.

File

Description

GRUB (/boot/grub)

Most commonly used bootloader package that loads the Linux kernel.

/etc/passwd

List of all local accounts.

/etc/shadow

Password hashes for all local accounts.

/etc/group

List of all local groups.

/etc/gshadow

Password hashes for local groups.

/proc/cmdline

Kernel parameters.

/etc/rc.*

Run commands.

/etc/profile

Sets system-wide environment variables on user shells.

/etc/hosts

Host-name-to-IP mappings—checked before DNS for name resolution.

/etc/resolv.conf

Lists DNS servers for system to use.

/etc/pam.d

Password and lockout policies.

~/.bash_profile, ~/.bash_login, ~/.profile, /home/user/.bashrc, /etc/bash.bash.rc, /etc/profile.d

Possible locations to insert a script that will run when the shell starts.

Note: For information on how to hack the GRUB bootloader, see https://null-byte.wonderhowto.com/how-to/hack-like-pro-linux-basics-for-aspiring-hacker-part-21-grub-bootloader-0154965/