It’s occured to me, many folks understand that WEP is easy to break, but don’t know all the steps and just how easy it is.  Here I hope to lay down the basic steps in one coherent post.. demonstrating how to crack into a wireless network using WEP, with a client attached to it.

Like always… only do this against your own networks.  The legal grounds are a bit grey here, but the ethical grounds are clear – you shouldn’t pick your neighbor’s doorlock.  Being a security professional also comes with the responsibility to use your skills for good, not evil.

Step 0: get the software.

I assume you’re using linux…. these tools do work on OSX but they require a bit of tweaking i think, and i haven’t done it myself.  so i’ll just write up linux.  you can use a VM of linux but the wireless card support is a bit flakier unless you’re using a USB card.

basically you only will need two packages, kismet, and aircrack-ng

So:
apt-get install kismet
apt-get install aircrack-ng

Step 1: Find a WEP network

Kismet is an amazingly powerful scanning tool and I could write much more about it than we need here.  It takes advantage of the feature in wireless cards to use “monitor mode”, which basically does passive listening for network traffic, and analyzes the traffic into a nice list.  It can do all sorts of other neat stuff like gps logging, etc, but that’s not totally necessary here.

If you don’t know it, you’ll need the interface name for your wireless card.  Check it by typing:

iwconfig
Then, just launch kismet (type ‘kismet‘) and then it will prompt you what your WLAN card is.  It will try and put it into monitor mode and is usually successful, even with built-in wireless.  If not theres some troubleshooting to be done….

Assuming it works, it will give you a list of networks it sees.  It ‘hops’ channels by switching the frequency the card is listening on and collects traffic on that frequency.  If there’s a WEP network in sight, kismet will highlight it in red, and you will need to pay attention to four things:

• Its BSSID – similar to the MAC address of the access point
• The ESSID – the ‘friendly name’ of the network
• The MAC address of a client that is attached to it.
• The channel the AP is broadcasting on

Kismet has a column that shows the amount of traffic it sees for both the AP in general and the client.  You want to target one with a client attached that is passing data… they’re the easiest targets.

An alternate path to WLAN monitor mode:

If kismet has a hard time putting your card into monitor mode, try running ‘airomon-ng start <interfacename>’ and it should attempt to do so.  If that still doesn’t work…. investigate getting a new card.  The Alfa AWUS306Hf is an excellent USB choice.

Step 2: prepare to attack

If it’s not setup yet, enable monitor mode:

airomon-ng start <interfacename>.

Begin a dump session – this logs traffic, sort of like a lightweight Wireshark.  You want to filter it to only the transactions we’re interested in:

airodump-ng –channel <c> –bssid <xx:xx:xx:xx:xx> –write <fileprefixname> <interfacename>

where c: the broadcast channel of the network
xx: BSSID of the network
<interfacename> – self explanatory (i.e. wlan0mon)

Keep this running and launch a new window for the next steps.

Step 3: do an ARP replay attack

This essentially looks for an ARP request from the attached client, and replays it many many times, enough to create a data set large enough to mount a cryptographic attack against WEP.

aireplay-ng –arpreplay -h <xx:xx:xx:xx:xx:xx> -b <yy:yy:yy:yy:yy:yy:> <interfacename>

where xx: the MAC address of the client
yy: BSSID of the network
<interfacename> – self explanatory (i.e. wlan0mon)

Once this has started, check out the other window.  You should see the data packets starting to increase rapidly.  When you’re at about 40k there is enough to crack a 104-bit WEP key.  The more the better, but no harm in starting early…

Step 4: mount the cryptographic attack

From the same directory you launched the dump process just run this:

aicrcrack-ng <fileprefixname>.cap -0

This will launch a window that shows progress.  if it’s successful, you’ll see the key!  if it’s not… keep waiting for more traffic.  40k+ data packets increases your odds tremendously but if it’s a simple WEP key it requires less.  This tool will actually keep trying as the packet capture increases in size so you can keep it running.  Or quit it (ctrl-c) and wait till you have more.

Step 5: connect!

If all went well you have broken the WEP key via the PTW attack method.  Now you can connect to the network.  Close down the dump sessions, etc etc and bring down your WLAN card – ifconfig wlan0 down

Then you’ve just gotta connect:
ifconfig <interface> up - bring up the wlan card

iwconfig <interface>mode managed key [WEP key]

iwconfig <interface> essid “[ESSID]” (Specify ESSID for the WLAN)

dhclient [interface] (to receive an IP address, netmask, DNS server and default gateway from the Access Point)

If all goes well you’ll get an IP and then you’re good to go, test by pinging or whatever else.

But if it didn’t work, they may have MAC filtering in place…

So change the MAC address of your wireless card to the same one that you just cracked with!  This is a bit messy and could freak out the DHCP server of the access point, but it’s worth a shot.

Bring the card down first:

ifconfig wlan0 down

Then change the MAC:

ifconfig wlan0 hw ether xx:xx:xx:xx:xx:xx

Bring it back up again and repeat.  You should be good to go.

This is a simplified walkthrough of a process that is documented many other places.  It should give you a taste of kismet, and the basics of the aircrack-ng suite, which has many many other great features.  I encourage you to read all about it over on their website.

Additionally, their site also contains a much more in-depth WEP crack tutorial.

Again, this is not ground-breaking, but it is always good to share the fundamentals in case someone hasn’t seen it before.  Good luck!

Continuing my small series on WLAN deployment strategy, now I’ll cover the two more uses for wireless networks in a business.

Segmented Mobile Data

Segmented Mobile Data networks can be found in retail environments for mobile point of sale, hospitals for critical bedside services, warehouses for inventory and logistics, or many other types of environments.  The main idea behind the use of a segmented mobile data network remains to isolate critical data; or to isolate weaker security technologies from the rest of the wireless network.  Regardless of the reasoning, the goal is the same: keep these networks separated from everyone else.  The most critical design decision, therefore, needs to be on the backend – deciding how exactly to segment these networks off.

Professional grade wireless infrastructure like the Cisco 5500 or Motorola RFS7000 is capable of two completely separated WLANs using the same equipment, which is a commonly used technique in such a design.  The infrastructure has an internal firewall that is used to prevent traffic from crossing between the two networks, and can use VLAN tagging to carry back to the main network using a shared WAN connection, or can use two entirely separate WAN connections.  Either way, the infrastructure is functioning as the separation device.  This also generally needs to be backed up with a firewall on the wired infrastructure side, restricting the data flows from the segmented WLAN into the enterprise.

Another alternative is to use two entirely separate pieces of hardware, with two separate physical connections back to the enterprise.  Depending on the needs of your organization, this may be required; if two physically separated wired LANs are deployed, bridging them with a WLAN device may not align with the networking vision.

The type of protection necessary for the the segmented data network again comes down to the technology available.  For data subject to technical compliance concerns, such as PCI-DSS or HIPAA, the stronger the better.  At minimum, WPA2-AES with pre-shared keys can suffice, although a certificate-based authentication solution is always preferable from a strict data security perspective.

If the network is being segmented due to equipment that cannot support strong encryption and authentication technologies, use the strongest available.  Unfortunately, many types of legacy equipment used in warehouses today cannot support WPA2-AES, or even WPA-TKIP – some may be stuck using WEP!  The weaker the level of protection, the more careful your segmentation on backend should be.

Guest Internet Access

Guest internet access generally is provided by a “hotspot”.  Users connect to an unencrypted network, and are sent to a captive portal page, where they can either login with pre-assigned credentials, or accept a terms of service and proceed without any credentials necessary.  Either way, authentication on such a network is accomplished only at the application-level, and there is no data protection provided by the WLAN itself.  As such, these networks should be treated as untrusted and kept firmly segmented from the enterprise, using the techniques described above.

A popular alternative deployment method for hotspot guest wireless networks is to use an entirely separate physical network for guests.  This can dramatically increase the infrastructure costs, but it accomplishes pure segmentation.  A typical use case for this type of physical segmentation would be a cafe or retail environment that wants to provide guests internet access, but doesn’t want to expose any of their business network.  Purchase a separate internet backhaul and configure a Wireless LAN dedicated to this network only.

If your business is subject to compliance regulations, such as PCI, I would strongly recommend using a physically segmented network for guest access.  While this increases capital expenses, it makes scoping activities related to compliance dramatically simpler.  When dealing with auditors, it is always advisable to have clear-cut boundaries around your critical data, and physically isolating any guest network is an easy way to do so.

Summary

Both of these network types rely on the network administrator segmenting the WLAN from the rest of the network.  It’s temping to plug an access point into an unmanaged switch and have the wireless “just work”, but this can open the network to many avenues of attack.  Assume the worse case at the beginning – that your WLAN is compromised – and design its place in the overall enterprise network to minimize the damage that an attacker could do from there.

Continuing my series on deployment strategies for enterprise WLAN, today I’m covering the most common type of WLAN deployment – extending the enterprise to mobile users.

Basic Enterprise Mobility – Strategy

Extending the enterprise’s wired LAN to wireless is one of the more straightforward tasks from a network design perspective, but the authentication piece for the Wireless LAN needs to be strictly controlled.  Fortunately, wireless can benefit from the widespread deployment of another technology in the enterprise world – centralized authentication servers.

Many enterprise environments utilize a centralized authentication system to manage their user accounts, with Microsoft Active Directory being one of the most common.  This system can also be leveraged to provide authentication to the Wireless LAN.  Active Directory can serve as an 802.1X authenticator, allowing the wireless network to use EAP technology to authenticate users.  The two EAP methods most worthy of consideration in a WLAN environment are EAP-TLS, and PEAP.

EAP-TLS provides full mutual authentication, using a public key infrastructure to create and manage certificates for both client devices and the authenticating server.  In practice, it will allow users to seamlessly authenticate to the wireless network, because the certificate exchange occurs behind the scenes.  In an Active Directory environment, the certificates used in authentication can be deployed remotely by the Domain Controllers.  This works especially well with laptop users, but can be a challenge with mobile devices that do not have a wired connection to the network.  Certificates can be pushed to mobile devices in several ways, such as by use of a dedicated management WLAN or physical installation via memory cards or barcode scanning, but in a large environment with many mobile devices, it may be wise to look into alternatives.

Fortunately, a worthy alternative to EAP-TLS exists with PEAP authentication.  PEAP provides for similar levels of security to EAP-TLS, but does not rely on client certificates to authenticate devices to the network.  Instead, PEAP uses a more traditional username & password combination.  These credentials can be integrated with an Active Directory environment, allowing administrators granular control over what users get access to the WLAN.  PEAP also mitigates the potentially expensive maintenance cost of managing certificates on mobile devices.

EAP-TLS and PEAP, combined with WPA2-AES, provide the strongest authentication and encryption solutions available in WLAN, and as such should be used to protect any critical data traveling over the network.  While integration with Active Directory is not mandatory, because many organizations have such an environment already deployed, extending its use to cover WLAN authentication is an attractive option.  If your organization does not have a centralized authentication system in place already, the deployment of a WLAN can be a strong motivation to do so.  Several free alternatives to Active Directory also exist, such as FreeRADIUS.  Some enterprise-grade WLAN infrastructure also provides the ability to generate and manage certificates using an internal server hosted on the access point.  Given the easy integration with common authentication systems, and the availability of free alternatives, there really is no reason not to deploy a centralized authentication solution to secure your enterprise WLAN.

Pre-Shared Keys – also known as “Personal” authentication – are generally not appropriate for enterprise environments.  WPA2-AES using pre-shared keys does not have any documented vulnerabilities, but any PSK solution relies on sharing authentication credentials between multiple users and devices.  This can affect the integrity of the network, and doesn’t provide any traceability to activities of users on the network.  It should be avoided in a mission-critical environment.

Continuing from my first post in the series, today I hope to cover the common use cases and general strategies for securing an enterprise WLAN.

Depending on the size and business needs of the enterprise, a WLAN can be used in a few different ways:

Basic Mobility – the most common use of WLAN is simply to extend the existing wired LAN to wireless users.  This can have a very positive impact on productivity, allowing users more flexibility throughout the workspace.

Segmented Mobile Data - this type of WLAN is one where the network is dedicated to use of a specific type of data that is segmented from the main enterprise network.  Typical use cases here are in hospitals or retail stores, where compliance regulations provide strict guidance on data protection and segmentation.

Guest Internet Access – common in cafes and large businesses, this type of WLAN typically provides only internet access and is entirely segmented from the enterprise wired LAN.

Wired LAN Replacement - this type of network is becoming a feasible alternative to the hassle of running cable, and will likely continue to grow in popularity as time goes by

These use cases can blend together in any number of ways.  A well thought-out design at the beginning, along with the right hardware planning, can accomidate these uses and even more.

General Strategy

Like other networking strategies, the use of proper segmentation at the Layer 2 level is critical when designing a WLAN.  Your most critical data flows should have their own segment, protected by methods like VLAN segmentation, firewalling, private IP spaces, and routing tables.  Regardless of the authentication and encryption method used for the WLAN itself, properly designing its location within the enterprise wired LAN is critical.

Data encryption in 802.11 is accomplished by a combination of the authentication type with an underlying encryption method.  Use of WPA2-AES encryption should be considered mandatory in any new WLAN deployment.  This encryption technology has no documented vulnerabilities and widespread hardware and software support.  If your enterprise has devices that do not support WPA2-AES, strongly consider replacing them.  When designing a network, its security should not be determined by the weakest link.  Unless there is a business case for doing something otherwise, use the strongest encryption and authentication methods available.

My next post will get into some specifics about these different use cases!

In the last decade, 802.11 Wireless LAN technology has had a dramatic impact on the technology world.  Reliable, high-bandwidth networking is now easily available to anybody who wants it, and the number of WiFi enabled devices continues to grow at a dramatic rate.  So naturally, businesses ranging from basic office environments, to complicated co-located warehousing/retail/office operations have begun leveraging the technology as well.  Unfortunately, the ease of setup that WLAN offers has led to some confusion among even seasoned IT practitioners.  In this series of  posts, I hope to provide some simple guidance to help clarify how to securely and efficiently manage an enterprise Wireless LAN.

Some History

I will not go into the history of the 802.11 standard in too much detail here, although there are a couple of important points to recognize when thinking about how to deploy a WLAN in your business.  The most important thing to know is this – many of the WLAN security technologies that were being used in deployment until three or four years ago are vulnerable to several well-known attacks.  If your business has a WLAN that has “just been working” for a while – it should probably get some attention.

To elaborate on this a bit further, the most common Wireless LAN encryption method used until late 2003, WEP, has been subject to some very public weaknesses, almost since its inception.  Its temporary replacement, WPA-TKIP, has similar (although not as dramatic) weaknesses, that have been public since at least 2008.

Adding insult to these platform-common weaknesses, some of the alternate, “more secure” based authentication methods advised by vendors have also been picked apart and had their vulnerabilities shown to the world.  I’m looking at you, LEAP.

To sum it up briefly – many networks that people thought were secure in 2003 or 2004 are definitely not secure today.  And unfortunately, WLAN sometimes is treated like a part of the physical infrastructure – if it ain’t broke, don’t fix it!

Current Tech

Fortunately, 802.11 is really starting to come into its own lately, and can be an extremely secure – in some ways more secure – piece of critical infrastructure.  The extremely solid (and so far unbroken) WPA2-AES encryption standard defined by 802.11i has had widespread vendor support since 2007.  And certificate-based authentication methods such as EAP-TLS, PEAP, and EAP-TTLS have similarly experienced a growth in support, among not just desktop OS platforms, but mobile operating systems as well.  And Wireless Intrusion Detection Systems are hitting their stride, ranging from several robust and effective professional solutions from vendors like AirTight, Cisco, and Motorola, to fantastic open-source applications like Kismet.  And robust infrastructure management software is now making the administration of Wireless LANs more simple and effective.

In short, today it is possible to deploy a WLAN that will meet all the use cases an enterprise can throw at it, and that is as secure as a typical wired LAN infrastructure.

In the next post, I’ll cover typical enterprise WLAN use cases, and the strategies for designing and securing them.

Several popular WLAN infrastructure vendors include lightweight RADIUS servers directly in their access points. These lightweight servers are typically designed for use by vendors as a backup solution in the event that connectivity to an off-board RADIUS server is lost.

I recently had the opportunity to speak with a WLAN network administrator and we briefly discussed the merits of using an integrated RADIUS server on APs vs using an external RADIUS server for authentication. After thinking about it for a few days, I realized that relying solely on the integrated RADIUS server for wireless authentication is rarely a good idea.

• Integrated RADIUS servers on APs are typically minimal servers that are designed to serve a small number of clients. If the WLAN network grows in size, the number of users that will need to be configured could easily exceed the limits of the integrated RADIUS servers.
• Some integrated RADIUS servers do not offer support for accounting services. This can be either a non-issue or a serious disadvantage depending on the purpose of the WLAN.
• Integrated RADIUS servers typically use proprietary local database engines/management interfaces to administer the user database, which makes it difficult to do certain operations like import/export user databases between APs or switch to APs from a different vendor.
• Standalone RADIUS servers offer advanced capabilities such as integrating with LDAP or Exchange servers to provide single sign-on capabilities. Integrated RADIUS servers in APs don’t have such capabilities due to the complexities and necessary protocol support required to interact with other authentication servers.
• Integrated RADIUS servers can only support the EAP methods that are built into it, restricting the set of EAP methods that can be used in the WLAN. Standalone RADIUS servers can typically support a much larger number of EAP methods and therefore provide the WLAN administrator with a great deal of flexibility. Note that APs which are acting only as a NAS are only relaying EAP messages between clients and the RADIUS server and therefore don’t need to have support for the different EAP types built-in.

However, even with all of the advantages a standalone RADIUS server offers over an integrated RADIUS server, there are some compelling advantages of the integrated solution: the integrated server is likely only to fail when the AP itself physically fails, the authentication sequence may be slightly faster since there is no extra hop between the AP and a RADIUS server, and of course it doesn’t require any additional capital expense for your network. In short, the decision between a integrated and standalone server solution should carefully consider short term and long term costs/network growth as well as flexibility in supporting both existing and future requirements of the network.

Wow – I would never have thought that in this day and age, a major vendor like Microsoft wouldn’t fully implement a spec.  However, in the case of WPA2 it looks like that they did exactly that – at least until 2005.

BUT making things more interesting- this was an “optional” update with XP SP2, until it was finally rolled into XP SP3.  There is a hotfix for XP SP2 machines in order to support WPA2 – KB 893357.

WPA2/AES didnt’ really become widely implemented until 2006, but it was in the 802.11i spec that introduced WPA in 2004.  For a major vendor like MS to not implement it is pretty crazy.  But then again I, as a wireless security professional, didn’t setup a WPA2/AES network in my home until last month.  So maybe they were onto something.

Anyways, if you’re using XPSP2 and a WPA2 network – you need the hotfix, or XPSP3+.  Good luck out there!  I really recommend moving to WPA2/AES, especially considering the improvements in the Nvidia CUDA drivers that are allowing TKIP to be broken in an increasingly short amount of time.

I’ve had the first commercially available Android mobile phone, the T-Mobile G1, since the platform launched last fall, and have been really happy with it so far.  As the platform is getting more mature, we are now starting to see a lot of new and useful applications out there – especially some useful for security!  Here’s a quick rundown of some of the tools that I’ve found and am using:

WifiScan – a great wireless discovery application for the platform.  It’s a powerful wireless audit tool that will log all of the discovered networks in range, and plot them to a KML file for visualization in Google Earth.  This application records information such as BSSID, Channel, Security Type, SSID, etc.  Tremendously useful for a discrete wireless network audit!

PortScandroid – a very basic port scanning application for the platform.  It’s not terribly useful for use over the cellular data network due to the filtering applied by T-Mobile, but when using 802.11, it gets the job done.  Doesn’t do any correlation of services to ports, but it performs the basic functions.

ConnectBot – this is a full-functioned SSH client for the platform.  Handy.

androidVNC – a VNC viewer for the Android platform that’s been forked from the tightVNC viewer development project.  Also a handy tool.  This is still in the beta phases and hasn’t been added to the Market yet, but it’s downloadable from the project page.  Easiest way to install it is to navigate to the project page within the phone’s browser and just download the APK package.

I am going to conduct a WarDriving contest between my little Android and a full-fledged laptop running Kismet and an external Wifi antenna to see how the signal discovery compares, but initial tests show the G1 to have a pretty remarkable Wifi range.  I’ll post a followup after I conduct the test.

The Android platform is showing a lot of promise, and for use on a pen-test, these tools could prove to be useful additions to your arsenal – and are certainly more discrete than using a laptop with a big ol’ antenna!

Thanks syn for inspiring me to investigate this – his post about the iPhone wireless toolkit made me wish we had these tools on the Android, and lo-and-behold – we do!