NMAP, known as the Network Mapper, is an open-source tool for network exploration, security auditing, and network scanning with capabilities such as host discovery, service and OS detection, version scanning, and vulnerabilities detection.
However, NMAP itself does not directly support passive analysis, as it is inherently an active scanning tool designed to interact with the devices it’s investigating. In other words, NMAP sends packets to a targeted network or system and then analyzes the responses to gather information. This whole process is active instead of passive (Source: NMAP website: https://nmap.org/book/intro.html).
Passive analysis, on the other hand, involves monitoring and collecting information about network traffic without directly interacting with the network systems or disrupting their operations. Here, tools such as Wireshark, Snort, and tcpdump are typically utilized as they silently listen to network traffic, record data, and analyze patterns without sending any packets themselves (Source: Wireshark documentation: https://www.wireshark.org/docs/wsug_html_chunked/ChapterIntroduction.html).
Nevertheless, NMAP can still be utilized in coordination with these passive tools to reinforce network security analysis. Once you have collected passive analysis data using a tool like Wireshark, you can use NMAP to actively verify and investigate potential security issues found during the passive analysis. For example, if your passive monitoring detected a suspicious behavior implicating a specific IP, you may use NMAP to scan the IP address to determine its open ports, running services, and potential vulnerabilities. Here is a quick command example: “nmap -A -T4 IP\_ADDRESS”
You may also want to take into consideration that while NMAP is an effective and powerful tool, its active scanning can be detected and stopped by firewalls, intrusion detection systems (IDS), and intrusion prevention systems (IPS). Therefore, NMAP provides stealth scan techniques that minimize the chance of being detected such as “-sS” flag for SYN scan and “-Pn” flag to avoid initial pings (Source: NMAP documentation – https://nmap.org/book/man-bypass-firewalls-ids.html).
In summary, while NMAP may not inherently support passive analysis, it plays an invaluable role in the overall process of perimeter security assessment when used in concert with passive analysis tools.
Sources:
1. NMAP’s official website: https://nmap.org/book/intro.html
2. Wireshark’s official documentation: https://www.wireshark.org/docs/wsug_html_chunked/ChapterIntroduction.html
3. NMAP Documentation: https://nmap.org/book/man-bypass-firewalls-ids.html
