Though enterprise-level solutions like AirMagnet Wi-Fi Analyzer and Ekahau Spectrum Analyzer have much more functionality, the free tools discussed here can be useful in a number of scenarios. For smaller networks, you might be able to get away with just using simple freeware tools for all of your Wi-Fi surveying needs. For larger wireless LANs (WLAN), these tools come in handy for a quick peek at the airwaves during design, deployment, or troubleshooting. (See screenshots from each of these products here.)
Each of these tools gives you the basic wireless details: SSIDs, signal strength, channels, MAC addresses, and security status. Some can even reveal "hidden" or non-broadcasted SSIDs, display the noise levels, or display statistics on successful and failed packets of your wireless connection. Two of the tools include Wi-Fi password cracking tools as well, useful for educational or penetration testing purposes.
Tarlogic Security offers Acrylic WiFi Free for non-commercial use, in addition to a paid/commercial version with more features. Both editions support a monitor or promiscuous mode to capture more traffic and have a built-in simple brute-force password cracking utility to test password security.
We found the free edition has a simple but attractive and user-friendly GUI. You always see the list of SSIDs and their details on the top portion of the application. Among the usual details, negative dBm values are shown for RSSI, it can distinguish 802.11ac, and it recognizes larger bandwidths and the multiple channels utilized. Any hidden SSIDs that are discovered from captured packets will be shown. For SSIDs with clients attached, you can expand that SSID on the list to see details of connected clients.
The application also has an inventory feature so you can assign and save names to detected SSIDs and/or clients, but the free edition limits you to five entries.
On the bottom portion of the application, you can tab between graphs and lists. One graph shows each SSID's signal strength and there's a graph for each band to help visualize channel usage and signal strength at the same time. There's a tab to see a list of clients that have specifically requested an SSID and then a tab to use when testing password security with its built-in bruteforce cracker.
There is no exporting or saving functionality for the details you capture, except for its unique Tweet feature that allows you to post a screenshot to Twitter.
Overall, Acrylic WiFi Free is a feature-rich Wi-Fi stumbler. It displays both textual and graphical details, great for simple Wi-Fi surveying needs as long as you don't need to save the data. Its hidden SSID and password cracking features are good bonuses.
AirGrab WiFi Radar is a free Mac-based Wi-Fi stumbler. Though optional, free registration is required to get rid of its snag screen.
The GUI displays the networks and graphs in a different way than most stumblers. On the upper left is a list of detected SSIDs with just its MAC address and channel. To see other details you must click on an entry. In addition to the usual details, WiFi Radar shows the noise level, which can be very helpful when doing wireless surveying or troubleshooting. On the upper right of the screen is the channel usage graph, which is displayed in a unique way.
If you don't mind the GUI of AirGrab WiFi Radar, it could be a useful tool for Wi-Fi surveying and troubleshooting, especially since it offers noise levels, allowing you to calculate the signal-to-noise ratio (SNR) of APs. Also convenient, both the network list and channel graph can be saved and exported.
Cain & Abel is a multi-purpose password recovery and cracking application that also features Wi-Fi stumbling, sniffing, and cracking tools. Like Acrylic WiFi, it also has a monitor or promiscuous mode to capture more traffic.
It has an older simplistic look and feel, with an old-style toolbar on the top with icons to bring up different utilities. The main portion of the application is tabbed; clicking the tabs shows the different utilities.
On the Wireless tab, you'll find the Wi-Fi stumbler. In addition to the typical SSID and signal info, you can see a list and details of connected clients. Plus for SSIDs and clients you'll find numbers on the amount of certain packets detected: all packets, unique WEP IVs, and ARP requests. Like Acrylic WiFi, any hidden SSIDs discovered from packets are revealed in the GUI as well. Most of status and data captured can be exported into a simple text file.
Due to the lack of graphs and inability to distinguish 802.11ac access points and larger channel-widths, Cain & Abel might not be a great choice for general Wi-Fi stumbling and surveying. But it certainly would be useful when performing penetration testing.
Homedale is a relatively simple and portable Windows-based stumbler with an optional command-line interface. Other than showing basic network and signal details, it supports GPS and other geo-location support logging.
This utility has a simple GUI that resembles more of a multi-tabbed dialog box than a full application. On the Access Points tab, you see all the usual details. Though 802.11ac is distinguished, it does show the multiple channels used by any SSIDs with larger channel-widths. However, it does not detect hidden SSIDs, though it does show their other network details.
Homedale offers a line graph of the signal levels for each SSID, but no graph is provided for visualizing channel usage. This tool might be most useful when a simple location-aware stumbler is needed, especially if you need to save or log the results.
LizardSystems offers a free edition of their Wi-Fi Scanner application for non-commercial use and a paid edition with more functionality. In addition to Wi-Fi stumbling, it displays statistics and graphics on certain types of packets for the network you're connected to. However, this is only available during the first 30 days of the free edition.
The application has a modern looking GUI that's easy to get around and understand. Two tabs switch between the screens for the stumbler functionality and the wireless information with packet details.
On the Scanner tab, you'll find a list of detected SSIDs. Along with the typical details, it shows signal strength in negative dBm values and percentages. Although it doesn't fully support 802.11ac, it does recognize their larger channel-widths. You can also use the list on the left to filter the SSIDs shown. On the bottom, you can flip between graphs showing signal levels and channel usage of the SSIDs, plus a scanner log.
On the Wireless Information tab, which is only available for 30 days in the free edition, you can see more details on your current wireless connection. This includes graphs and statistics on many different Mac layer and PHY layer packets types.
Overall, Wi-Fi Scanner would be an okay tool for general surveying needs, keeping in mind it won't allow you to save or export the findings, reveal hidden SSIDs, nor fully recognize 802.11ac. It has a user-friendly GUI with capabilities to filter the types of access points should be shown.
The WirelessNetView utility is freeware from NirSoft, offered for personal or commercial purposes. It's a very simple Windows-based Wi-Fi stumbler, available in an installable or portable download.
For the signal strength, it shows negative dBm values and for percentages, it shows values for the last signal received and the average over time. Another unique detail it offers is how often each SSID has been detected, which could be useful in certain situations. All this data can be exported to a simple text file.
Keep in mind, this utility lacks advanced features, like graphs, hidden SSID detection, full 802.11ac support, and recognizing all channels for access points utilizing larger channel-widths. However, it still might be useful for simple Wi-Fi stumbling, especially if you need to save or export the findings.
In Mac OS X Mountain Lion 10.8.4 and later, Apple provides the Wireless Diagnostics tool. It's more than just a stumbler; it can help you detect and fix Wi-Fi issues as well. Best of all, it's a native tool included with the OS.
To get started, press the Option key and then click the Airport/Wi-Fi icon on the top of Mac OS X. This displays some more details on your current Wi-Fi connection while also making the Wireless Diagnostics shortcut available.
When you open Wireless Diagnostics, it will begin running tests to detect any issues, which you could utilize if there are issues. Otherwise you can choose Window > Utilities to access the other wireless tools. You can see the current connection and environment details, perform frame captures, configure logging, scan for network details, and view performance information, including noise and SNR values.
For more info, Apple provides a great tour and tutorial on Wireless Diagnostics.
Eric Geier is a freelance tech writer--keep up with his writings on Facebook or Twitter. He's also the founder of NoWiresSecurity providing a cloud-based Wi-Fi security service, and On Spot Techs providing RF site surveying and other IT services.