Performance Objective

At the conclusion of the course the student will be able to:

  1. Identify what Shodan is.

  2. Explain how to search with Shodan.

  3. Explain how to build an alternative to Shodan.

  4. Explain where Shodan is often used in the hacking time line.

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Shodan is a search engine for internet connected devices. It allows you to explore the internet, see a big picture, gain a competitive advantage, or monitor network security. The Shodan search engine is simple to use and should be familiar to most internet users. It functions in a manner similar to Google, DuckDuckGo, or other search engine. You can look for specific items or search for keywords.

How does Shodan Work

Shodan themselves have declared that they use a ‘home-grown, distributed port scanner’ in order to search the internet. There exist approximately 4,294,967,296 (four billion two hundred ninety-four million nine hundred sixty-seven thousand two hundred ninety-six) IPv4 Addresses. This pool is 32-bits in size. Scanning these addresses is an embarrassingly parallel workload and can be easily distributed over any number of systems. The term embarrassingly parallel simply means that little or no effort is needed to separate this problem into a number of parallel tasks. Password cracking and 3d video rendering are also examples of this type of problem.

Is Shodan Illegal?

I am not a lawyer and I am not your lawyer.

The Computer Fraud and Abuse Act is a computer trespass statute that could potentially come into play when using Shodan or Masscan within the United States. Widespread Scanning could fall into several provisions revolving around scanning.

  1. “intentionally access a computer without authorization or exceed authorized access, and thereby obtain … information from any protected computer[.]”

  2. “knowingly cause the transmission of a program, information, code, or command, and as a result of such conduct, intentionally cause damage without authorization, to a protected computer[.]”

  3. “intentionally access a protected computer without authorization, and as a result of such conduct, recklessly cause damage[.]”

  4. “intentionally access a protected computer without authorization, and as a result of such conduct, cause damage and loss[.]”

The CFAA functions as both civil as well as criminal statute and violations can result in criminal prosecution, fines, and prison time. Private parties harmed by violations can sue for injunctive relief (force people to do something) or for money.

So is Shodan or Masscan a case of intentionally accessing a protected computer without authorization that could cause harm or loss? It depends on if a prosecutor is interested in causing you harm. Laws like the CFAA are in place to allow for enforcement discretion or selective enforcement.

Prosecutors hold wide latitude in deciding when, who, how, or even whether they should prosecute for violations of this crime. If they decide that your scanning is an affront to someone of note, you will find yourself in court.

Shodan is probably safer than Masscan as you are moving the burden of performing the scanning from your control to someone else.

Why use Shodan

Not every one has the knowledge and resources to use tools like masscan to replace Shodan. It can be a daunting task to install Elastic Search, deploy Masscan, parse the results, upload to their server, and then search and peer through the data. Shodan simplifies this mess by doing all of the heavy lifting for you.


Publicly available information is the best tool for developing an attack plan. Your initial efforts should be spent long on preparation and research. Shodan is a good tool for discovering weaknesses or potential areas for exploitation.

First we install dnsutils so we get access to the host command.

$ sudo pacman -S dnsutils

Run the host command on

$ host

Run a whois on the IP and pipe to less.

$ whois|less

Running the Host Command

The resulting CIDR: is our network range we want to scope out using Shodan.

Go to Shodan and type in net: into the search.

Total Results: 912

All Results In The United States with most in Round Rock / Austin TX area.

Top Services:

  • HTTP
  • SSH
  • NTP
  • DNS

Operating Systems:

  • Windows 7 or 8 is 11
  • Linux 2.6.x is 2

Top Products:

  • Microsoft IIS httpd
  • Apache
  • Microsoft HTTPAPI httpd
  • ntpd
  • OpenSS

Another interesting check might be port 27960. Go to Shodan and use port:27960 to see how many Quake servers are potentially online.

Other searches can include -


  • postal:85225


  • apache city:austin


  • vnc country:US


  • nginx hostname:'google'


  • cisco net:'IP/24'


  • https os:windows


  • port:27960


  • title:"Chandler Police Department"


  • html:"Chandler Police Department"

How a search for the Windows OS looks.

Honey Pots

A honey pot is a software suite or server configuration designed to appear vulnerable but is instead intended to allow a defender the ability to review and watch what an attacked may be doing. The idea being that you can learn much from an attacker who is operating at full capacity against what they believe to be a vulnerable system. An extensive list of honey pots can be found on Github.

Many honey pots can be defeated with the use of the cat command. Some servers will use generic defaults that can be added to a script for reviewing a server. You can quickly cat a file like /etc/passwd and see if it matches the same as the contents found in the honey pot configuration. If the two items match then you can assume the system is a honey pot and disconnect immediately.

$ cat /etc/passwd

This is not ALWAYS the case but can be a safe rule of thumb and simple check.

Business Intelligence

Created a product and need to know who is using it in an insecure manner? You can easily run searches for your product or port and keep a running tally of all public facing instances of your product. You could do this to your competitor as well and potentially find companies who need your ‘assistance’.

Target Acquisition

Shodan provides plenty of information about the makeup of the internet. As so far as we are allowed to know. Some testing reveals that Shodan appears to employ a list similar to the masscan-exclude list compiled byrjmolesa. This exclusion list includes networks for Government Agencies, FBI Honeypots, Military Targets, and more.

Shodan does a good job of respecting exclude lists and you can contact their support team to request to be added to their ignore list.

Does an exclusion list also double as a Very Important Target list?

ICS Radar


Bacnet (port 47808)

DNP3 (port 20000)

EtherNet/IP (port 44818)

Niagara Fox (ports 1911 and 4911)

IEC-104 (port 2404)

Red Lion (port 789)

Modbus (port 502)

Siemens S7 (port 102) (PDF)

Big Data

Elastic Stack is vulnerable to ransom ware.

The NFL Elastic Stack was breached.

Exactis was breached and their elastic search server leaked.

How to build a Shodan alternative


Elastic Stack

$ masscan -p80,21,22,23,25,110,143,443,3389,U:161 --banners --rate 1500000 -oB ccc-shodan.scan --exclude

Ok. But does it do practical things?

There are 9,248,986 potentially vulnerable NTP servers on Earth at this moment.

You can easily find the vulnerable servers in a city.

Attacking with NTP Step 1

Verify they are running NTP and have an open port of 123.

Attacking with NTP Step 2

Deploy the use of a simple python script to create an NTP Amplification DDOS.

Attacking with NTP Step 3

A script for NTP DDOS is here.

Adding or using vulnerable IOT botnets would increase your capability immensely.


  1. Shodan is a search engine for internet connected devices. It provides information such as ports, banners, and is an excellent source of intelligence on the current state of the internet.

  2. A simple search for open ports, devices, or program names can be conducted directly from the Shodan web page in a manner similar to how Google, DuckDuckGo, or other search engines function.

  3. You can build your own version of Shodan using tools like Masscan in combination with Elastic Search.

  4. Shodan is useful when you are trying to perform reconnaissance.

A word on vocabulary

Is Shodan OSINT or SIGINT?

OSINT or Open Source Intelligence is the gathering of data from open source or readily and freely available sources.

SIGINT or Signals Intelligence is the act of gathering information in transit by interception.

I believe Shodan is OSINT when in use by researchers and SIGINT when deployed by the company themselves.


Shodan is an excellent tool for searching the internet when you do not have the capability to perform the search yourself. Using Shodan frees you from the infrastructure management and liability that could come from running Masscan from a server you own. Shodan is a simple to use tool that protects the user from reprisal but also poses security dilemmas itself. Shodan requires an account for some searching, logs users, and is also able to study information such as what is being searched, clicked on, or viewed. You should not rely on Shodan for any reason in which you could possibly be met with reprisal as it is an opaque box.

Ultimately Shodan is a beneficial tool that allows you to conduct deep and telling reconnaissance of a target all while never firing off a packet yourself. It is not fool proof and requires an account which therefore generates an audit log. You should not use Shodan if you are worried about an audit of your use.

Final Recommendations

  1. Use Linux.

  2. Learn tools but also learn how those tools work.

  3. Practice.

  4. Document.