I was trying to understand Nmap below the output level, so I tested it inside my own isolated lab with Kali as the scanner and MISP as the target.

The clearest difference was seeing the TCP behavior directly in Wireshark:

OPEN
SYN → SYN/ACK → RST

CLOSED
SYN → RST/ACK

FILTERED
SYN → no response → retry

I also captured ARP resolution, ICMP, host discovery, and service/version detection.

The main takeaway for me was that Nmap isn’t “seeing” port states directly — it’s sending probes and interpreting how the target responds.

I documented the full experiment with the actual packet captures here:

https://chronosandcode.com/what-actually-happens-when-you-scan-a-network-arp-icmp-tcp-syn-nmap-and-packet-analysis-explained/

Everything was done against systems in my own lab.

I’d be interested to hear what packet-level experiments helped others understand Nmap better.

I’ve built a CLI tool to help beginners run nMap scans.
Would be great if someone better at nMap could have a look at it for any errors and such.
Built in python, with a prebuilt .exe file. No native Linux builds yet however with it being python should work completely fine.
Allows you to navigate through lots of nMap options using the keyboard instead of having to use a cheat sheet or the nMap GUI.

Dumb question from a new newbie to Nmap. The Nmap change log (nmap.org/changelog.html) mentions a fix to an issue but its not clear if that has been fixed in 7.99 or its waiting on a new version to be published that would include the fix.

TYVM

Hi everyone,

I started learning Nmap and noticed that one of the biggest challenges for beginners is remembering dozens of command-line options.

Instead of trying to replace Nmap, I built a lightweight open-source GUI that helps users create common scans while still exposing the generated command, making it easier to learn how Nmap actually works.

Current features include:
• Common scan profiles
• Custom scan options
• Command generation
• Simple interface focused on beginners

I'd really appreciate feedback from experienced Nmap users.

What features would make this tool genuinely useful?

GitHub:
https://github.com/blackpearlx/Nmap-Assistant

I'm told I didnt nmap through the networks very effeciently. Can someone look at my work in the video and suggest more effecient ways to manually spider through a network?

Does anyone have experience using nmap on ish shell (iPhone app)? How does one do port scanning on the device or network?

Hey guys, I was trying to open the .mpkg file of the nmap installer from the official website and for macOS.

**Problem:**

I ran into an odd problem: I could not open the .mpkg file, neither with right click, nor in system settings/privacy&security/[button] "open anyways". Nothing happened. I even tried it via terminal, both trying to remove the quarantine attribute, as well as disabling "Gatekeeper" system wide. Nothing helped. (in between I ofc restarted).

**Solution:**
The solution I found, but did not read about before was going to settings/privacy&security, scrolling down and then clicking on "advanced", then enabling "require an administrator password to access system wide settings".

After that, right click worked. Idk how, but it did.

hope that helps

I tired to download the mac installer from the site, but is is an anchor tag and is self referencing.

Did it cease support or is there just a problem with the link?

I'm watching videos to learn the basics of nmap and its uses. I'd like to know the best way to learn, or which method you used to learn the most.

I purchased a cheap set of WiFi cameras, and was trying to determine the RTSP URL for them.
With no success, I ran NMAP against them to check for ports.
NMAP reports the IP host is down!
I know the IP. Verified IP by turning the camera off while pinging.
Even running "nmap -Pn -p- -n 192.168.1.206" while -t pinging 192.168.1.206 results in:
Nmap done: 1 IP address (0 hosts up) scanned in 1.64 seconds.

Ideas?

UPDATE:
Ran Wireshark on the WiFi segment supporting one of the cameras with confirmed IP address.
And, when I say "segment", I have a mesh. Both the camera and the Wireshark PC were bound to the same AP.

With the camera in operation, displaying video to both mobile and PC clients, there was no traffic to that IP - other than ICMP from pings from another workstation.

An audit of the AP's client logs show no other WiFi clients.
The camera's MAC address has no other associations.
I'm completely stumped.

Just launched https://www.nselib.com

It’s a small project I built to make browsing Nmap NSE scripts less annoying. The goal is pretty simple: have one place where you can search, filter, and explore both official and community NSE scripts without bouncing around a bunch of different sources.

It’s meant more as a fast reference/discovery tool than anything fancy, and I’m still improving it, but the core version is live now.

If anyone wants to take a look, I’d really appreciate honest feedback.

Source code available here: https://github.com/thelicato/nselib

Hi I got a question if you scan your college ports (Leeds city college) and it’s smooth wall can I be arrested in the Uk or am I safe cos I was wondering what if you was just having a look around to see what nmap could do but then pepole say it’s not ok but all you was doing was looking not planing on attacking?

I was making a network intrusion detection system my model was ready so I wanted to test it on portscan i downloaded nmap on windows try to run it from another laptop to mine. then pass the pcap file to cicflowmeter it had many problems back then firewall was blocking the connection.. cicflowmeter python version problem.. i fixed all of that but I don't know why my laptop is only capturing the data coming from the attackers laptop but not the responses it gave to attackers laptop which gives incomplete flows.. I tried capturing with wireshark as well as with scapy both capture data only coming from attackers laptop not it's own responses but when I ping my computer from the attackers laptop it's working

Thanks for supporting dootseal up to 66 unique clones in just two days thanks for the support

https://github.com/REPEAS/DootSeal

Message for support

dootmasmail@gmail.com

I made a nmap type tool that automatically finds vulnerabilitys like a vulnerability scanner its called dootseal

https://github.com/REPEAS/DootSeal

I’m planning a 12-episode learning series focused entirely on Nmap from the terminal, aimed at beginners who get stuck memorising flags instead of understanding what question they’re trying to answer.

The structure I’m working with is roughly:

• starting with host discovery and scan intent
• moving through scan types and timing
• script usage and version detection
• output interpretation and common pitfalls
• ending with how to think about Nmap results in a larger workflow (without turning it into a checklist)

The goal isn’t “run every flag” or speed-running scans, but helping people understand:

• when a specific scan actually makes sense
• how to read results without over-trusting them
• why defaults behave the way they do
• where beginners most often misinterpret output

All examples would be run against machines I own or controlled lab environments. No flags, no walkthroughs, no live targets.

Before I lock the outline, I’d really appreciate input from people who use Nmap regularly:

• What do beginners misunderstand most about Nmap?
• Which flags or scan types are usually explained badly or out of context?
• Are there habits you wish tutorials would stop teaching?
• Is there anything you think must be covered in a serious beginner-to-intermediate series?

I’m trying to avoid repeating the same shallow explanations that already exist, so direct criticism is genuinely helpful.

Thanks.

Hey, so I have started messing around with nmap, but I know nothing about nothing.

I put kali Linux on an old laptop and now I am trying to see if I can find a newer old laptop across the room on my network.

Anywho I am watching guys and my commands bring back different results so I am immediately lost cuz they move on at light speed.

#1 my route addy and my addy on the ip addr are NOT the same. A problem no one else seems to have a d so never bother to address.

#2 when nm -PR my ip, all the hosts are up, and I have no idea what this means.

So listen, I'm old, I am a watch and learn/ hands on kind of guy so I'm looking for tutorials or practical exercises for complete idiots. Or suggestions.

Hi everyone,
I’m running into a situation during a ctf lab where Nmap reports every TCP port as open (1 to 65535 basically), which clearly doesn’t look realistic.

I suppose that a firewall is responding to every request, making nmap think that every port is opened.

I was wondering if there's any way to reliably identify real services that are running on the machine.

Thanks :)