Cyber Security Internship - Task 1

Scan Your Local Network for Open Ports

Objective

The objective of this task was to perform a TCP SYN scan on the local network using Nmap to identify active hosts, discover open ports, understand the services running on those ports, and analyze potential security risks.

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Tools Used

• Nmap
• Windows Command Prompt
• GitHub

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Procedure

Step 1: Installed Nmap

Downloaded and installed Nmap from the official website.

Step 2: Identified Local Network Range

Used the following command:

ipconfig

The local network range was identified and masked for privacy.

Example:

192.168.x.0/24

Step 3: Performed TCP SYN Scan

Executed the following command:

nmap -sS 192.168.x.0/24

Step 4: Saved Scan Results

nmap -sS 192.168.x.0/24 -oN scan_results.txt

Step 5: Analyzed Results

The scan identified active hosts and their open TCP ports within the local network.

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Sample Masked Scan Output

Starting Nmap 7.xx

Nmap scan report for 192.168.x.1
Host is up.

PORT      STATE SERVICE
53/tcp    open  domain
80/tcp    open  http
443/tcp   open  https

Nmap scan report for 192.168.x.10
Host is up.

PORT      STATE SERVICE
135/tcp   open  msrpc
139/tcp   open  netbios-ssn
445/tcp   open  microsoft-ds

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Common Ports and Services

Port	Service	Description
22	SSH	Secure Remote Login
53	DNS	Domain Name Service
80	HTTP	Web Server
135	RPC	Windows Remote Procedure Call
139	NetBIOS	Windows File Sharing
443	HTTPS	Secure Web Traffic
445	SMB	Windows File Sharing

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Potential Security Risks

• Unauthorized access through exposed services.
• Exploitation of outdated or vulnerable applications.
• Information disclosure.
• Malware propagation across the network.
• Increased attack surface.

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Security Recommendations

• Close unnecessary ports.
• Enable and configure firewalls.
• Keep operating systems and software updated.
• Disable unused services.
• Use strong passwords and authentication.
• Monitor network activity regularly.

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Interview Questions

1. What is an open port?

An open port is a network communication endpoint that is actively accepting incoming connections.

2. How does Nmap perform a TCP SYN scan?

Nmap sends a SYN packet to a target port. If the target responds with a SYN-ACK packet, the port is considered open. Nmap then sends an RST packet instead of completing the connection.

3. What risks are associated with open ports?

Open ports can expose services that attackers may exploit to gain unauthorized access or gather information.

4. Explain the difference between TCP and UDP scanning.

TCP scanning checks connection-oriented services, while UDP scanning checks connectionless services and is generally slower due to the lack of acknowledgements.

5. How can open ports be secured?

Unused ports should be closed, firewalls should be configured properly, unnecessary services should be disabled, and systems should be kept updated.

6. What is a firewall's role regarding ports?

A firewall controls incoming and outgoing network traffic by allowing or blocking access to specific ports based on security rules.

7. What is a port scan and why do attackers perform it?

A port scan is the process of identifying open ports and services on a device. Attackers use port scanning to discover potential vulnerabilities and entry points.

8. How does Wireshark complement port scanning?

Wireshark captures and analyzes network packets, allowing users to inspect traffic generated during port scans and troubleshoot network communication.

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Outcome

Successfully performed a TCP SYN scan using Nmap, identified active hosts and open ports, understood the services running on those ports, and gained practical knowledge of network reconnaissance and basic network security.

Note: Local IP addresses have been masked to protect network privacy.