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July 14, 2026

I Scanned The Entire Internet Port Range In Under 6 Minutes. Here Is How

A beginner-friendly, no-fluff guide to mastering Masscan for real-world recon

By Yamini Yadav_369

7 min read

The first time someone told me Masscan could scan all 65535 ports on a target in seconds, I did not believe it. I had spent years running Nmap scans that took forever on large IP ranges, and I just assumed that was the price you pay for thorough port scanning.

Then I actually ran Masscan on a client's entire subnet during an external VAPT engagement. What normally took Nmap over an hour finished in under two minutes. I sat there staring at the terminal thinking I had done something wrong. I had not. That is just how fast Masscan really is.

If you work in security and you are still only using Nmap for large scale port scanning, you are leaving a lot of speed on the table. This post breaks down exactly what Masscan is, how it works differently from other scanners, and every important command explained in plain English so you can start using it properly today.

What Is Masscan

Masscan is a free and open source port scanner built for one purpose, raw speed at massive scale. It was created by Robert David Graham, and its whole design philosophy is simple. Scan huge IP ranges and huge port ranges as fast as physically possible over the network.

Think of Nmap like a careful inspector walking through every room of a building, checking each door, testing the locks, noting details. Masscan is more like a drone flying over an entire city in minutes, just checking which doors are open and which are shut. It does not care about details yet, it just wants to know what is open so you know where to look closer later.

Security engineers, red teamers, and researchers use Masscan when the target is too large for traditional tools to scan in reasonable time. Think entire company IP ranges, cloud provider subnets, or even internet wide research scans.

Why Masscan Even Matters

Most companies think of firewalls and open ports as something they already control. In reality, cloud environments spin up new servers constantly, and each new server can accidentally expose ports to the internet without anyone noticing right away.

If a company has thousands of IP addresses across its cloud infrastructure, checking each one manually or even with Nmap becomes painfully slow. Masscan gives you the ability to sweep that entire range quickly and find exposed ports before an attacker does.

Speed here is not just convenience. In large engagements with tight timelines, being able to scan a massive range in minutes instead of hours can be the difference between covering the full scope properly or missing critical exposed services.

How Masscan Actually Works

Understanding the engine behind Masscan will help you use it far more effectively, so let us slow down here.

Its own custom TCP stack: Unlike most scanners that rely on the operating system's normal networking stack, Masscan built its own TCP stack from scratch. This is the real secret behind its speed. It bypasses a lot of the overhead your OS normally adds when handling network connections.

Asynchronous scanning: Masscan does not wait for one connection to finish before starting the next one. It fires off packets asynchronously, meaning it sends thousands of probes out and just listens for whatever responses come back, without holding up the process waiting on each individual target.

Stateless design: Traditional scanners keep track of the state of every connection they open. Masscan mostly skips this. It sends a SYN packet and just waits to see if a SYN-ACK comes back, and that is enough information to know a port is open. This stateless approach is what allows it to blast through huge ranges so fast.

Rate control: Because Masscan can technically send millions of packets per second, it lets you control exactly how fast you want to go. This rate control is important because going too fast can crash weak network equipment or trigger every alarm bell on a target's monitoring systems.

Installing Masscan

On Kali Linux, Masscan usually comes preinstalled. If not, install it with:

sudo apt install masscan

To build from source for the latest version:

git clone https://github.com/robertdavidgraham/masscan
cd masscan
make

Check your installation:

masscan --version

If a version number shows up, you are ready to scan.

This is the part most guides rush through. I am going to slow down and explain each command properly so you actually understand what you are telling the tool to do.

1. Basic single port scan

Command:

masscan 192.168.1.0/24 -p80

What it means in plain English: "Check every IP address in this range and tell me which ones have port 80 open."

When to use it: Good starting point when you just want to know which machines in a range are running a web server.

2. Scanning multiple specific ports

Command:

masscan 192.168.1.0/24 -p80,443,8080

What it means: "Check this whole IP range but only look at ports 80, 443, and 8080."

When to use it: Useful when you already know which services you care about and want to save time by not scanning every port.

3. Scanning the entire port range

Command:

masscan 192.168.1.0/24 -p0-65535

What it means: "Check every single port from 0 to 65535 on every IP in this range."

When to use it: This is the real power move of Masscan. Full port range scans on large networks are usually too slow for other tools, but Masscan handles it in a fraction of the time.

4. Controlling scan speed

Command:

masscan 192.168.1.0/24 -p80,443 --rate 1000

What it means: "Do the scan, but only send 1000 packets per second instead of going full speed."

When to use it: Always control your rate on client engagements. Going too fast without permission can look like a denial of service attack and can crash older network devices. Start slow and increase gradually if you have clearance.

5. Saving results to a file

Command:

masscan 192.168.1.0/24 -p1-1000 -oL results.txt

What it means: "Do the scan and save the results in a simple list format into results.txt instead of just printing to my screen."

When to use it: Always, so you can review findings later, compare across scans, or feed results into other tools.

6. Saving results in JSON format

Command:

masscan 192.168.1.0/24 -p1-1000 -oJ results.json

What it means: "Same scan, but save the output in JSON format so it is easier to parse with scripts or other automation tools."

When to use it: Great when you plan to feed this data into a script, dashboard, or another tool that reads JSON easily.

7. Scanning from a list of targets

Command:

masscan -iL targets.txt -p80,443

What it means: "Instead of typing one IP range, read the list of targets from this text file and scan them for ports 80 and 443."

When to use it: Perfect for large engagements where you already have a defined scope list of IPs or subnets to test.

8. Excluding certain IPs from the scan

Command:

masscan 192.168.1.0/24 -p80 --excludefile exclude.txt

What it means: "Scan this range but skip any IP addresses listed inside exclude.txt."

When to use it: Very important when certain systems in scope are fragile, out of bounds, or explicitly excluded by the client. Never skip this step if you have an exclusion list.

9. Setting a custom source port

Command:

masscan 192.168.1.0/24 -p80 --source-port 61000

What it means: "Send all my scan packets out using port 61000 as the source instead of a random one."

When to use it: Sometimes useful when you need scan traffic to be more predictable for firewall rules or when troubleshooting network filtering during a scan.

10. Banner grabbing

Command:

masscan 192.168.1.0/24 -p80,22 --banners

What it means: "Check these ports, and if they are open, also try to grab any banner or version information the service reveals."

When to use it: Extremely useful for quickly identifying what software and version is running on an open port without a separate tool.

11. Using an interface and router details for accuracy

Command:

masscan 192.168.1.0/24 -p80 --interface eth0 --router-mac aa:bb:cc:dd:ee:ff

What it means: "Send scan traffic out through this specific network interface and use this router's MAC address so packets route correctly."

When to use it: Needed in certain network setups, especially when scanning from a machine with multiple interfaces or unusual routing where Masscan cannot automatically detect the correct path.

12. Doing a practice run without sending packets

Command:

masscan 192.168.1.0/24 -p80 --echo

What it means: "Show me exactly what configuration you are about to use for this scan before you actually send anything."

When to use it: Great for double checking your command syntax and settings on a big scan before committing, especially useful when you are still learning the flags.

None

Here is how I actually use Masscan on a real engagement, step by step.

  1. Confirm scope and get the exclusion list from the client before touching anything.
  2. Run a full port range scan across the entire authorized IP range with a controlled rate, saving output to a file.
  3. Review the open ports found and identify anything unusual or unexpected, like a database port facing the internet.
  4. Take that narrowed down list of interesting IPs and ports, then run a focused Nmap scan on just those for deeper service detection and version fingerprinting.
  5. Document everything with timestamps for the report, since fast wide scans followed by focused deep scans is the combination that actually works well in practice.

Masscan finds where to look. Nmap tells you what is actually there. Using them together like this is far more effective than trying to force one tool to do the whole job.

The biggest mistake is running Masscan at full speed without setting a rate limit. Masscan can send an enormous number of packets per second by default, and doing this on a client network without warning can look exactly like a denial of service attack. Always start with a conservative rate.

Another common mistake is forgetting the exclusion list. If a client tells you certain systems are off limits, that exclusion file is not optional, it is a requirement. Skipping it can cause serious problems, both technically and legally.

Many beginners also treat Masscan results as final. Remember, Masscan tells you a port is open, but it does very little to identify what is actually running on it in detail. Always follow up with a proper service detection tool like Nmap on the interesting findings.

Masscan is not trying to replace Nmap, and it should not be used that way. It is built to solve a completely different problem, scanning speed at massive scale. Once you understand that it trades depth for speed by design, you stop expecting it to do Nmap's job and start using it the way it was actually meant to be used, as the fast first pass that tells you exactly where to point your deeper tools next.

Learn to control your rate, always respect exclusion lists, and pair Masscan with a proper follow up scan. Do this consistently and your recon on large scale networks will be faster and sharper than most people testing the same scope.

If this helped you understand Masscan better, follow The First Digit for more practical security tool breakdowns written the way they should be, simple, honest, and based on real testing experience.