On Linux and UNIX-like systems, files or directories that begin with a period (.) are considered hidden. These files do not appear by default when a user runs the ls command, unless explicitly instructed to show hidden files using ls -a.
Example:
File named .hiddenfile will not appear with a simple ls command.
To view it, use: ls -a
This is commonly used for configuration files (e.g., .bashrc, .profile) and also by attackers or malicious users who want to conceal their scripts or payloads.
Incorrect Options:
A. Exclamation mark (!) is used in shell history and command expansion, not for hiding files.
B. Underscore (_) is a valid filename character but does not hide files.
C. Tilde (~) represents the current user's home directory; not used for hiding.
Reference – CEH v13 Official Courseware:
Module 06: Malware Threats
Section: “Tactics to Hide Malware Files in the OS”
Lab: CEH Engage — Creating and Hiding Files in Linux
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