Active Recon
TCP and UDP are fundamental protocols that govern communication across networks, but they differ in their approach:
TCP (Transmission Control Protocol):
Connection-oriented: Establishes a virtual connection between two devices before data transmission, ensuring reliable and ordered delivery.
Reliable: Uses error checking and retransmission mechanisms to guarantee data arrives correctly and in sequence.
Slower: The connection setup and error checking introduce some overhead, making it slightly slower than UDP.
Suitable for: Applications that require reliable data transfer, like web browsing, file transfer, and email.
UDP (User Datagram Protocol):
Connectionless: Sends data packets (datagrams) directly without establishing a connection, making it faster and simpler.
Unreliable: Doesn't guarantee delivery or order of packets. Applications need to implement their own error checking if needed.
Faster: Lower overhead due to the lack of connection setup and error checking.
Suitable for: Applications that prioritize speed over reliability, like online gaming, live streaming, and DNS lookups.
Scanning TCP and UDP Ports:
Port scanning involves sending packets to specific ports on a target device to see if they are open (listening for connections) or closed (not accepting connections). Here's how it works:
Specify Target: You provide the IP address of the target device.
Select Ports: Define the range of ports you want to scan (common ports or custom ranges).
Protocol Choice: Choose between TCP or UDP scan depending on the type of service you're looking for.
Scan Initiated: The scanning tool sends packets to each port on the target device.
Response Analysis: The tool analyzes the response from the target device to determine if the port is open, closed, or filtered (firewalls might block the scan attempt).
Tools for Port Scanning:
Several tools are available for scanning TCP and UDP ports. Here are a few popular options:
Nmap (Network Mapper): A free and open-source network security scanner with a vast array of features, including TCP and UDP port scanning. It offers various scan types, customization options, and powerful reporting capabilities. https://nmap.org/
Nessus: A commercial vulnerability scanner with a comprehensive set of features, including TCP and UDP port scanning. It goes beyond basic port scanning to identify potential vulnerabilities on the target device. https://www.tenable.com/products/nessus/nessus-professional
Angry IP Scanner: A free and easy-to-use tool for basic TCP and UDP port scanning. It provides a quick overview of open ports on a target device. https://angryip.org/download/
Netcat (nc): A versatile command-line networking tool that can be used for various purposes, including basic TCP and UDP port scanning. https://docs.oracle.com/cd/E86824_01/html/E54763/netcat-1.html
Network Scanning and Host Discovery:
Nmap:
Nmap is a versatile open-source tool used for network scanning and host discovery. It can identify open ports, services, and OS details. Usage example:
nmap -sS -p 1-65535 -T4 -A target_ip.
Masscan:
Masscan is a high-speed network scanner that can scan the entire internet in under six minutes. Usage example:
masscan -p1-65535 target_ip.
Angry IP Scanner:
Angry IP Scanner is a lightweight and cross-platform network scanner for discovering active hosts. Usage example: Enter the target IP range and click "Start."
Sparta:
Sparta is a Python tool that combines multiple scanning and enumeration tools to simplify the information-gathering process.
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