WEEK1-Writeup

 Linux Command Line Interface (CLI) Fundamentals

Basic Navigation & File Operations

• ls - List directory contents with various flags (-la, -lh, -R)

• cd - Change directory (absolute vs relative paths)

• pwd - Print working directory

• cp - Copy files and directories

• mv - Move/rename files and directories

• rm - Remove files and directories (-r, -f flags)

• mkdir - Create directories (-p for parent directories)

• cat - Concatenate and display files

• tac - Display files in reverse

• head/tail - View beginning/end of files

• more/less - Page through file content

File Viewing & Manipulation

• grep - Pattern searching (-i, -v, -r, -E, -l)

• find - Search for files (-name, -type, -size, -exec)

• locate - Find files using database

• which/whereis - Find command locations

• man - Manual pages

• apropos - Search man pages

• sudo - Execute as superuser

• su - Switch user

Package Management

• apt - Debian/Ubuntu package management (install, update, upgrade, remove)

• yum/dnf - RHEL/CentOS package management

• dpkg - Debian package management

 Bash Scripting

Core Concepts

• Shebang (#!/bin/bash)

• Variables declaration and usage

• Command substitution ($(), ` `)

• Passing arguments ($1, $2, $@, $#)

• Reading user input (read)

Control Structures

• If/else/elif statements

• For loops

• While loops

• Until loops

• Case statements

• Functions definition and calling

• Return values and exit codes

Advanced Scripting

• String manipulation

• Arithmetic operations

• Arrays

• File testing (-f, -d, -r, -w, -x)

• Redirection (>, >>, 2>, &>, |)

• Here documents (<<)

 Linux File Permissions & User Management

Basic Permissions

• Understanding permission notation (rwx)

• Numeric permissions (octal: 755, 644, etc.)

• chmod - Change file permissions

• chown - Change file owner/group

• chgrp - Change group ownership

• umask - Default permission mask

Special Permissions

• SUID (Set User ID) - chmod u+s

• SGID (Set Group ID) - chmod g+s

• Sticky Bit - chmod +t

• Identifying and exploiting misconfigured permissions

User & Group Management

• /etc/passwd structure

• /etc/shadow structure

• /etc/group structure

• useradd/usermod/userdel

• groupadd/groupmod/groupdel

• passwd - Change passwords

• id - Display user/group IDs

 Networking Basics

Network Configuration

• ip - Modern network configuration

• ifconfig - Legacy interface configuration

• route - View/modify routing tables

• /etc/network/interfaces and /etc/resolv.conf

Network Diagnostics

• ping - ICMP echo requests

• traceroute/tracepath - Trace network path

• netstat - Network statistics (-tulpn flags)

• ss - Socket statistics (modern netstat replacement)

• dig - DNS lookup utility

• nslookup - Query DNS servers

• host - DNS lookup utility

• arp - ARP table manipulation

Netcat Mastery

Basic Operations

• Connect to TCP/UDP ports: nc <host> <port>

• Listen on ports: nc -lvnp <port>

• File transfer (sender/receiver)

• Port scanning with Netcat

Advanced Usage

• Banner grabbing: echo "" | nc -nv <host> <port>

• Reverse/bind shells

• Proxy and relay setup

• Chat server creation

 Information Gathering Techniques

Domain Intelligence

• whois - Domain registration information

• Understanding whois record components (registrar, nameservers, dates)

Google Hacking (Dorking)

• Basic operators: site:, inurl:, intitle:, filetype:

• Advanced operators: intext:, cache:, link:

• Combination operators for specific findings

• Google hacking database (GHDB) familiarity

DNS Enumeration

• dig with various record types (A, MX, TXT, NS, SOA)

• Zone transfers with dig (AXFR)

• dnsenum - Comprehensive DNS enumeration

• dnsrecon - Advanced DNS reconnaissance

• Subdomain enumeration techniques

 Nmap Port Scanning

Scan Types

• TCP Connect Scan (-sT)

• SYN Stealth Scan (-sS)

• UDP Scan (-sU)

• ACK Scan (-sA)

• Window Scan (-sW)

• Maimon Scan (-sM)

Advanced Options

• Service Version Detection (-sV)

• OS Detection (-O)

• Script Scanning (-sC)

• Timing Templates (-T0 to -T5)

• Output Formats (-oN, -oX, -oG)

Practical Scans

• Full port scan: nmap -p- <target>

• Top ports scan: nmap --top-ports 1000 <target>

• Comprehensive scan: nmap -sC -sV -O <target>

• Firewall/IDS evasion techniques

• NSE (Nmap Scripting Engine) usage

 Service Enumeration

SMB Enumeration

• smbclient - SMB file sharing

• smbmap - SMB share enumeration

• enum4linux - Comprehensive SMB enumeration

• Nmap SMB scripts (smb-os-discovery, smb-enum-shares)

SMTP Enumeration

• Manual SMTP commands (HELO, VRFY, EXPN, RCPT TO)

• smtp-user-enum - SMTP user enumeration

• Nmap SMTP scripts (smtp-commands, smtp-enum-users)

SNMP Enumeration

• snmpwalk - SNMP tree walking

• snmp-check - SNMP enumeration tool

• Common SNMP community strings

• MIB (Management Information Base) concepts

 Practice & Hands-On

TryHackMe Rooms

• Complete “Linux Fundamentals” room

• Complete “Network Services” room

• Complete “Bash Scripting” room

• Practice in “Nmap” room

Vulnerable VMs

• Set up and scan Metasploitable 2

• Practice against Kioptrix series

• Use VulnHub machines for real-world practice

OffSec Labs You Can use THM OR HTB

• Whois Enumeration lab

• Google Hacking lab

• Netcraft lab

• DNS Enumeration lab

• TCP/UDP Port Scanning lab

• SMB/SMTP/SNMP Enumeration labs

 Final Validation

• Can navigate Linux filesystem without GUI

• Can write basic to intermediate Bash scripts

• Understand and can modify file permissions

• Can perform comprehensive network enumeration

• Can conduct full Nmap scans and interpret results

• Can enumerate common services (SMB/SMTP/SNMP)

• Have practiced on at least 3 vulnerable VMs

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You can find me online at:

• X (Twitter): Md3omer
• GitHub: Mhdomer
• LinkedIn: mhd3omar
• Tryhackme: nonlouy