Network infrastructures are constantly under threat from hackers and cyber attacks, putting companies at risk of reputational damage and financial loss. To combat these threats, network engineers have a range of tools at their disposal, one of which is Nmap, or Network Mapper. Nmap is a free, open source tool used for network discovery and audits, and its versatility makes it invaluable to network administrators, pen testers, ethical hackers, and unfortunately, even malicious hackers.
One of the most powerful features of Nmap is its Nmap Scripting Engine (NSE), which allows users to write scripts to automate various network tasks. These scripts are written in Lua, an embedded programming language, and can be used to perform network reconnaissance and discover vulnerabilities. And that’s where Nmap comes in.
Network reconnaissance is the first stage of the Cyber Kill Chain model, a framework developed by Lockheed Martin to trace the stages of a cyber attack. During this stage, network teams gather information about potential attack targets, and Nmap is a commonly used tool for this purpose. By conducting scans, Nmap can determine what is running on a computer or network, including open ports, services, and applications. It achieves this by establishing a TCP connection using Internet Control Message Protocol (ICMP), TCP, or User Datagram Protocol (UDP) messages.
Nmap offers various scanning techniques, but let’s delve into four of the most common types:
1. TCP SYN scan: This stealth scan is used to determine if ports on a target system are open, closed, or filtered. Nmap sends a SYN packet to the target and waits for a response. If the target responds with a SYN/ACK packet, the port is considered open. If it responds with an RST packet, the port is closed.
2. Version detection scan: This scan gathers details about the services and applications running on identified open ports. By sending probes to open ports, Nmap can receive responses from the services on those ports, providing information about the types of services running.
3. OS detection scan: This scan helps determine which operating system (OS) a target network or computer is running. Nmap sends TCP packets with specific characteristics to the target host and determines the OS based on the host’s responses. Advanced options of the scan can also detect the specific OS version and potential security risks.
4. Vulnerability scan: This scan detects Common Vulnerabilities and Exposures (CVEs) to discover if a target is vulnerable to attacks. It skips a ping scan and runs vulnerability detection scripts against the target host. This scan can help network admins identify and address vulnerabilities before they are exploited by malicious actors.
However, it’s important to note that network scanning should only be conducted with proper authorization and within the confines of legal and security frameworks. Unauthorized scanning can have serious consequences, so network admins should always ensure they have proper permission before running Nmap scans.
To ensure successful network vulnerability discovery, it’s essential to follow best practices:
1. Choose the right tool: Before conducting a scan, it’s important to select the tool that best suits your needs. Nmap is a popular choice due to its accuracy.
2. Plan the scan: Communicate with stakeholders to establish clear goals, scope, and duration for the scan. Without proper planning, unexpected results may arise.
3. Run the scan: Select the type of scan, target IP address, IP address range (if applicable), and vulnerabilities to detect.
4. Scan frequently: Refer to company policy to determine how often and what to scan. Regular scanning helps to identify and address vulnerabilities in a timely manner.
5. Analyze the vulnerabilities: Review the scan results and assess the severity of each CVE to prioritize and address the most significant risks.
6. Document the scan: Documenting each scan is crucial for future reference and understanding. It helps teams compare scans and track changes over time.
In conclusion, Nmap is a powerful tool for network vulnerability discovery. By utilizing its various scanning techniques, network teams can detect potential points of entry for cyber attacks and address vulnerabilities before they are exploited. However, it is of utmost importance to obtain proper authorization and follow best practices to ensure a safe and legally compliant scanning process. With careful planning and analysis, Nmap can play a significant role in maintaining secure and resilient network infrastructures.