The following is the final part of a six-part series on wireless security. Each tip is excerpted from the Cisco Press book, Network Security First-step by Tom M. Thomas. Check back frequently for the next installment, or go to the main series page for all installments.
Essential wireless hacking tools
This section examines some of the tools that eliminate some of the threats discussed in the preceding sections. In theory, these tools were all designed to help network administrators take care of their networks, and they are still touted as such on each website. In reality, these are some of the same tools that attackers can and will use; thus, network administrators should also use them to ensure that their wireless networks are secure.
Wireless networking is everywhere! That is not meant as hyperbole—it really is everywhere. Wireless technology uses radio waves to transmit data, so wireless packets are probably flowing in the air in front of you as you read this.
As everyone knows by now, where wireless packets flow, wireless access points are pumping them out (where there is smoke, there is fire). If only there was a way to find out whether any WAPs were nearby. Fortunately (and unfortunately), there is a way to discover just that.
A little piece of freeware called Net Stumbler is available on the Internet (found at: http://www.netstumbler.com/) that provides you with such secret pieces of information as the following:
- WAP's SSID (Service Set Identification, the unique name you can assign to your WAP)
- Signal strength of the discovered WAPs and whether the WAP is using WEP
What channel the WAP is transmitting on, and some other sneaky bits of information
NetStumbler is also available for Apple computers in the form of an application known as MacStumbler (http://www.macstumbler.com).
You might have even seen NetStumbler make an appearance on the local evening news under the headline, "Wireless Security Threats: You Could Be Next!" or some other scary tagline. Figure 8-7 shows the NetStumbler interface.
NetStumbler sends out a broadcast on all channels looking for a response. If your WAP is configured to respond to the broadcast (SSID broadcast "enabled" setting), NetStumbler logs that WAP and furnishes you with a "bing-bing" tone designating a target. A word of caution, however: NetStumbler can lock only onto 802.11b and some 802.11a-compliant WAPs.
The truth is that NetStumbler does not tell you much more than your wireless NIC's configuration interface. However, the trick is that NetStumbler tells you all the information you need about someone else's wireless network.
Most wireless NIC configuration programs allow you to perform a site survey, which sniffs around for other wireless access points that are configured to broadcast on the same channel as your NIC. If you happen to find a WAP with the default SSID (in this case, the default SSID of a Linksys WAP is "linksys") displayed, you can assume that you can connect to that WAP with little or no trouble.
One of the best features about NetStumbler is its capability to integrate laptop-based GPS units into its WAP discovery adventure. Imagine driving along with your trusty laptop on the passenger seat of your POV (privately owned vehicle) and hearing the pleasant "bing-bing" tones generated by NetStumbler as it happily sniffs out WAPs within transmitting distance. Every time that your laptop makes that sound, NetStumbler queries the attached GPS unit and records the coordinates of the WAP it found. Later, you can download the coordinates into mapping software and have a nice, little map printed out to show you where the WAPs were found. And who says technology doesn't make our lives just a wee bit more interesting?
The whole GPS issue aside, NetStumbler is not actually a hacking tool because the information it reveals is just a step above what your NIC can already help you find out. Tools like NetStumbler are more along the lines of a "reconnaissance" tool because they help you discover things that might not have been immediately obvious. One mission that NetStumbler has recently been assigned is that of Rogue AP detector.
Wireless Packet Sniffers
Sniffing packets can be both fun and profitable if you know how and what to sniff. Any network administrator can lay his hands on a packet sniffer in a matter of seconds and snag a couple of hundred packets before you can even read this paragraph. The contents of these packets can reveal network secrets that have been closely guarded. "Sniffing," or "snarffing" in the HaXoR world, is the process of intercepting and recording traffic that was never supposed to be seen by anyone other than the sender or receiver.
To the layman, the idea of "sniffing," "capturing," or "snagging" packets is an alien concept; therefore, the basics of the operation deserve some brief discussion:
- Packets travel over an Ethernet connection from source to destination.
- A NIC set to "promiscuous" mode can "listen in" on all local traffic.
- A packet "sniffer" can see and record all this traffic.
- A packet "sniffer" can also decode the packet and display neat things like the source MAC address, the destination MAC address, and the data payload contained in the packet.
- Packets contain things like unencrypted Windows LanMan v.1 passwords, passwords sent in clear text, and other tasty things relished by hackers.
Now that you know about wired packet sniffers, you also need to meet their wireless cousins. How is this possible, you ask? Can I really capture wirelesss packet traffic? Could it be that easy? Do hackers know about this? The answers are, yes, yes, and yes.
Yes, hackers know about sniffing wireless connections, and they have made the most of it. Have you turned on a MAC filter on your WAP? Packet captures rat you out by telling the hacker the MAC address' source. It is easy to spoof a MAC address on your wireless NIC, especially with a program called SMAC, lovingly created by a group of guys at KLC Consulting. They make both a Win32 and Linux version of the software that virtually (as in not actually, but makes it appear so) changes your NIC's MAC address. If a hacker "sniffs" your wireless packets, he can decode the packets, read the MAC address of a machine listed in the WAP's MAC filter, plug that number in SMAC, and impersonate a machine that is authorized to use the WAP. It can do all this in less than one minute. That is correct—60 seconds. In the time it takes to dip a biscuit in gravy and eat it, a hacker can intrude on your network. But what if I am running WEP, you might ask? Read the following section and save your question for later (http://www.wildpackets.com/products/airopeek_nx).
Now you understand more about the encryption used by WEP, how WEP does its thing, and how wireless is vulnerable. Things were going along swimmingly back in the year 2001 for the wireless world—until a piece of software called AirSNORT came along. The 802.11 protocol was under attack and that attack continues even today.
AirSNORT made its first widespread public appearance in the pages of Wired magazine on August 20, 2001. The concept of snagging packets and cracking the encryption protecting them was not a new concept; in fact, security experts had known of WEP's weaknesses for quite a while. The AirSNORT software was merely the hacker's "combo meal" that put the capture and the cracker in one easy to use application. The downside to AirSNORT was that it ran only on Linux (and still does today), which did not have nearly the level of acceptance that it does today.
The people who invented AirSNORT were interviewed at the time of release and professed that it was not written with the intention of it becoming a staple in the hacker toy box; rather, it was intended to be a proof of concept tool that demonstrated the inherent weakness of WEP.
It is estimated that AirSNORT needs to capture only five or six million packets and chew on them for as little as a minute, or as long as a couple of hours, before it can chew through the encryption and reveal the WEP key. Those time estimates were unbelievable in 2001. Can you imagine how much faster today's 2- and 3-gigahertz machines can mow through the same amount of data? Can you say s-e-c-o-n-d-s? From an attacker's point of view, the downside of this is that it can take a long time to gather the millions of packets necessary—but once they do?
As if this were not bad news enough for would-be wireless warriors, another piece of software called WEPcrack popped on the radar screen at the same. WEPcrack did roughly the same job as AirSNORT, but it was not as far along in the development phase. You can find AirSNORT at: http://airsnort.shmoo.com/.
Other wireless tools such as KisMET and KisMAC, which are wireless AP locators and include support for GPS location and positioning, can be used to create maps of all known, open wireless access points in a city.
Reproduced from the book Network Security First-step, ISBN 1587200996, Copyright 2004, Cisco Systems, Inc. Reproduced by permission of Pearson Education, Inc., 800 East 96th Street, Indianapolis, IN 46240. Written permission from Pearson Education, Inc. is required for all other uses. Visit www.ciscopress.com for a detailed description and to learn how to purchase this title.
About the book
With the proliferation of Internet viruses and worms, many people and companies are considering increasing their network security. But first, you need to make sense of the complex world of hackers, viruses, and the tools to combat them. Network Security First-step explains the basics of the core technologies that make up and control network security.
Author Thomas M. Thomas, II, CCNA, CCNP, CCDA, CCIE No. 9360 is a certified Cisco Systems instructor and the founder of NetCerts.com and the Certified Professional Association – Worldwide, an organization designed to bring together the users of Cisco equipment to learn and network. He was previously a course developer and instructor, and has published several titles on Cisco networking. Tom is currently working as a Senior Principle Consultant with Ericsson IP Infrastructure.