Network Scanning

Core Technology

Article from Issue 202/2017
Author(s):

Network scanning may carry a negative connotation, but it doesn't mean you shouldn't look for weak spots in your network.

Imagine you are administering a small office or home network. Perhaps you want to know what hosts in this subnet are currently online, or which service that Internet of Things (IoT) device keeps open to the world. Network scanners are tools built to do just that.

Even if a host is properly secured and has unused ports closed, a network scanner may tell quite a lot about it. There are slight discrepancies in how popular operating systems (OSs) implement network protocols such as TCP. A tool that knows these nuances can make an educated guess about which OS the host runs. This is known as OS fingerprinting, and many network scanners implement it as well. Sometimes, it can even give you an uptime estimate!

As you guessed already, this Core Tech is about network scanning. Before we dive in, a usual word of warning: As with many technologies, network scanning can be used for good and for evil. Many network attacks begin with it, so it is deemed illegal in some provider and corporate networks. Never scan a network you don't really own unless you have permission to do so. When in doubt, a purpose-built scan target, scanme.nmap.org, is a good choice.

[...]

Use Express-Checkout link below to read the full article (PDF).

Buy this article as PDF

Express-Checkout as PDF
Price $2.95
(incl. VAT)

Buy Linux Magazine

SINGLE ISSUES
 
SUBSCRIPTIONS
 
TABLET & SMARTPHONE APPS
Get it on Google Play

US / Canada

Get it on Google Play

UK / Australia

Related content

  • Nmap Workshop

    In "The Matrix Reloaded," Trinity uses Nmap to hack into the power grid to pave Neo's way to the architect of the virtual world. However, the port scanner is also ideal for more mundane purposes – such as discovering vulnerabilities in your domestic network.

  • Nmap Methods

    How does the popular Nmap scanner identify holes in network security? In this article, we examine some Nmap analysis techniques.

  • Nmap Scripting

    Nmap is rolling out a new scripting engine to automatically investigate vulnerabilities that turn up in a security scan. We’ll show you how to protect your network with Nmap and NSE.

  • Nmap 4.75 recognizes iPhones and visualizes networks

    "If we are going to call Nmap the 'Network Mapper', it should at least be able to draw you a map of the network! " writes developer Fyodor in announcing the newest version 4.75 of the Nmap security scanner.

  • Charly's Column

    Many tools keep growing with each new version, but Nmap 4.00 has lost weight thanks to the Diet-Nmap project. The latest incarnation of Nmap is not only quicker, it is also more frugal with memory.

comments powered by Disqus
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters

Support Our Work

Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.

Learn More

News