ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

Firewall Probing with Zenmap

Updated on August 23, 2011

Introduction

Zenmap is a graphical frontend for the command line program "nmap". Zenmap is available for Windows, Linux, FreeBSD, and Mac OSX. To learn more, and to download Zenmap, visit http://nmap.org/zenmap/

You can use Zenmap/nmap to scan computers or other devices on a network for vulnerabilities. You can use it to determine what ports are open and closed on your devices, and to monitor how much information your machines are broadcasting. Because of this, Zenmap is an excellent tool for monitoring and securing your network and its attached devices.

I have linked a screencast of myself demonstrating Zenmap at the bottom of this page. If you are a visual learner and want to skip all of the writing, feel free to. The video is available up to 720p, and the text is quite legible when you fullscreen it.

1) Choosing a Target

The first step is to determine the target you wish to scan. You will get the most accurate results from servers that are located on the same network as you are. The more devices there are between you and the target device, and depending on the types of devices between you, the less accurate your results are going to be. The reason for this is that, especially when traversing over the internet, you are "probably" only going to be scanning the gateway that filters internet traffic to hosts on a larger network, rather than the computer you want to scan.

So what you want to do is set your network up so that you have as few devices between yourself and the target as possible. In the "target" box, enter the IP address of the host you wish to scan. You can also use hostnames, but to lower the risk of DNS resolution problems, I always use the IP address.

Target -> Type of Scan -> Execute

Nmap Done

2) Choosing and Executing the Scan

There are several different types of scans available in Zenmap that allow you different options. You can do a quick scan, an intense scan, and intense scan without ping, etc. The type of scan you choose depends on your desired results. For most cases, an "Intense Scan" should suffice, unless the destination machine does not respond to ping. In the event that the target does not respond to ping, the scan will terminate early. If this happens, but you know the target is reachable and just not responding to a ping, use the scan type "Intense Scan, no ping".

Once you have entered the target's IP and selected the type of scan, click the "Scan" button to begin the scan. Depending on the speed of your network, the distance between you and the target, and the nature of the scan, it could take several minutes for the scan to complete. What you want to watch for in the main tab (Labeled Nmap Output) is the string of text "Nmap done". Once you see that, it's time to review our results.

Review the Results

Probably the most important thing I use Zenmap for is testing my firewalls. Once the scan has completed, the other tabs in the Zenmap interface will now be filled with information.

The "Ports / Hosts" tab of the interface will now list all of the ports discovered on the target, their status, and if available, the service and software listening on those ports. This tab is very handy for determining if a port you opened is actually open, or if you have ports open that should not be open.

The "Topology" tab effectively illustrates a "Traceroute" between you and the target, using a circular diagram. The more devices between you, the bigger and more complex the diagram will become. You can also save the diagram as a PNG image to your computer.

The "Host Details" tab will list things such as the type of operating system, uptime, the last time the target was rebooted, MAC address, IP address, and a summary of how many ports were found and in what state they were found.

Scans can also be saved in XML format so they can be re-opened later for review on other computers, or for your own record keeping purposes.

Summary

Zenmap is a free, open source, and powerful tool to help you monitor and improve the security of your networks and devices.

I have recorded a video of myself demonstrating the use of Zenmap below if you want some visual assistance in understanding what you're looking at.

I hope you find this walkthrough helpful. Comment with your suggestions below and I'll try to make sure I implement them in future articles.

Zenmap Demonstration

Comments

    0 of 8192 characters used
    Post Comment

    • skear profile image

      Sam Kear 

      7 years ago from Kansas City

      Nice video! Nmap is a very useful utility, many people have no idea there is a gui for it.

    working

    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, hubpages.com uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: https://hubpages.com/privacy-policy#gdpr

    Show Details
    Necessary
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
    Features
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Marketing
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Statistics
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)