Scanning Tools

Scanning Tools in Network Scanning - CEH Guide

Understanding Scanning Tools for CEH Exam

Scanning tools are essential components in the ethical hacking toolkit, serving as the primary means through which security professionals identify potential entry points and vulnerabilities in target systems. This guide will help you understand scanning tools, their importance, functionality, and how to excel in exam questions related to them.

Why Scanning Tools are Important

Scanning tools allow ethical hackers to:
- Discover active hosts on a network
- Identify open ports and services running on target systems
- Map network topology and architecture
- Detect operating systems and application versions (fingerprinting)
- Identify potential security gaps before malicious actors do
- Gather intelligence for more targeted penetration testing

In the security assessment lifecycle, scanning represents the critical phase between initial reconnaissance and actual exploitation attempts.

Common Scanning Tools You Must Know

1. Nmap (Network Mapper)
The most versatile and widely used scanning tool. Key features include:
- Port scanning with multiple techniques (SYN, FIN, XMAS, etc.)
- OS detection
- Service version detection
- Script engine for vulnerability assessment
- Network mapping

Example syntax: nmap -sS -A -T4 192.168.1.0/24

2. Nessus
A comprehensive vulnerability scanner that:
- Identifies known vulnerabilities
- Performs compliance checks
- Offers remediation suggestions
- Provides detailed reporting

3. Hping
Advanced packet crafting tool used for:
- Custom TCP/IP packet generation
- Firewall testing
- Port scanning
- Network testing

4. Masscan
Extremely fast port scanner capable of scanning the entire Internet in under 6 minutes.

5. Nikto
Web server scanner that checks for:
- Outdated server software
- Dangerous files/CGIs
- Server configuration issues

6. Angry IP Scanner
Simple but effective tool for:
- Rapid IP range scanning
- Ping sweeping
- Port scanning

7. Unicornscan
Specialized for:
- Asynchronous stateless TCP scanning
- Efficient network reconnaissance

8. Zenmap
The GUI version of Nmap with:
- Visual network mapping
- Scan profiles for beginners
- Scan comparison features

How Scanning Tools Work

Most scanning tools operate by sending specially crafted packets to target systems and analyzing the responses (or lack thereof). The main techniques include:

Port Scanning Techniques:
- TCP SYN Scan: Sends SYN packets and analyzes SYN-ACK responses
- TCP Connect Scan: Completes the full TCP three-way handshake
- UDP Scan: Sends UDP packets to detect open UDP ports
- FIN/XMAS/NULL Scans: Uses abnormal flag combinations to evade simple filters
- ACK Scan: Used to map firewall rulesets

Host Discovery Methods:
- ICMP Echo: Simple ping requests
- ARP Scanning: For local network discovery
- TCP/UDP Sweeping: Sending packets to common ports

Service and OS Detection:
- Analyzing response headers and behaviors
- Banner grabbing
- Protocol-specific probes

Exam Tips: Answering Questions on Scanning Tools

1. Know the Specific Use Cases
Memorize what each tool is best used for. Exams often present scenarios asking which tool is most appropriate.

2. Remember Common Syntax
The CEH exam may ask about specific command options, especially for Nmap. Know common switches like:
- -sS (SYN scan)
- -sT (Connect scan)
- -sU (UDP scan)
- -O (OS detection)
- -sV (service version detection)

3. Understand Output Interpretation
Practice reading scan results and understanding what they mean. Questions may show output and ask you to interpret it.

4. Distinguish Between Scanning Types
Know the difference between:
- Port scanning
- Vulnerability scanning
- Network mapping
- Banner grabbing

5. Stealth vs. Aggressive Scanning
Understand which techniques are considered stealthy and which might trigger IDS/IPS systems.

6. Common Port Numbers
Memorize standard ports for common services (HTTP-80, HTTPS-443, FTP-21, SSH-22, etc.).

7. Scanning Defense Mechanisms
Know how firewalls, IDS/IPS, and other security measures detect and block scanning attempts.

8. Limitations of Each Tool
Understand what each tool cannot do as well as what it can do.

Practice Scenario Questions

When answering scenario-based questions:

1. Identify the goal of the scanning activity in the scenario
2. Consider the constraints (time, stealth requirements, target type)
3. Select the most appropriate tool and technique
4. For command syntax questions, pay attention to exactly what information the command should gather

Remember that in real-world situations and in the exam, the ethical hacking process requires proper authorization and adherence to legal boundaries. Scanning tools should only be used against systems you have permission to test.