1. Wireless Security

2. ECE 4112 - Internetwork Security
Agenda
Basics of an Attack
802.11b Overview
WEP
Other security measures
Future of Wireless Security
Basics & Overview – Blake
WEP – Varun
Sec. Measures & Future of Wireless – T. Matt Guinn
Lab Overview – Matt Condit
ECE Internetwork Security

3. ECE 4112 - Internetwork Security
Step 1: War Driving
Materials needed: Laptop w/ b card and GPS, Netstumbler, Airsnort, Ethereal, and the car of your choice
An attacker would first use Netstumbler to drive around and map out active wireless networks
Netstumbler not only has the ability to monitor all active networks in the area, but it also integrates with a GPS to map AP’s
ECE Internetwork Security

4. Step 2: Cracking Using Airsnort
At this point, the attacker has chosen his target; most likely a business
Netstumbler can tell you whether or not the network is encrypted
If encrypted, park the car, start up Airsnort, and leave it be for a few hours
Airsnort, given enough time, will passively listen to traffic and figure out the encryption key
ECE Internetwork Security

5. Step 3: Listening to the Network
Once the encryption key is compromised, it is a trivial process to connect to the network, and if there wasn’t an encryption key at all, well then ….
An attacker would next use Ethereal to listen to the network traffic, analyze, and plan further attacks
ECE Internetwork Security

6. That’s it…the network is compromised
Most wireless networks are no more secure than this, many are less secure
Hundreds of business’s, schools, airports, and residences use wireless technology as a major point of access to their networks
Growth of demand for Wireless LANs (WLAN) is increasing dramatically
ECE Internetwork Security

7. ECE 4112 - Internetwork Security
Basic b Overview
802.11b was IEEE approved in 1999
Infrastructure Mode or Ad Hoc
Utilizes 2.4GHz band on 15 different channels (only 11 in US)
11mbit shared among all users on access point
Cheap!!!
ECE Internetwork Security

8. Built in Security Features
Service Set Identifier (SSID)
Differentiates one access point from another
SSID is sent in ‘beacon frames’ every few seconds.
Beacon frames are in plain text!
ECE Internetwork Security

9. Do’s and Don'ts for SSID’s
Default SSID’s are well known (Linksys AP’s default to linksys, CISCO defaults to tsunami, etc) so change them immediately.
Don’t set your SSID to something that will give away information.
Do change the settings on your AP so that it does not broadcast the SSID in the beacon frame.
ECE Internetwork Security

10. Associating with the AP
Access points have two ways of initiating communication with a client
Shared Key or Open Key authentication
Open key allows anyone to start a conversation with the AP
Shared Key is supposed to add an extra layer of security by requiring authentication info as soon as one associates
ECE Internetwork Security

11. How Shared Key Auth. works
Client begins by sending an association request to the AP
AP responds with a challenge text (unencrypted)
Client, using the proper WEP key, encrypts text and sends it back to the AP
If properly encrypted, AP allows communication with the client
ECE Internetwork Security

12. Is Open or Shared Key more secure?
Ironically enough, Open key is the answer in short
Using passive sniffing, one can gather 2 of the three variables needed in Shared Key authentication: challenge text and the encrypted challenge text
Simply plugging these two values into the RC4 equations will yield the WEP key!
ECE Internetwork Security

13. Wired Equivalent Protocol (WEP)
Primary built security for protocol
Uses 40bit RC4 encryption
Intended to make wireless as secure as a wired network
Unfortunately, since ratification of the standard, RC4 has been proven insecure, leaving the protocol wide open for attack
ECE Internetwork Security

14. ECE 4112 - Internetwork Security
A closer look at WEP
Weakness in RC4 lies within the Initialization Vector (IV)
The IV is a random 24bit number (2^24)
Packets sent over the network contain the IV followed by the encrypted data
RC4 combines the IV and the 40bit key to encrypt the data
Two known attacks against this!
ECE Internetwork Security

15. Numerical Limitation Attack
IV’s are only 24bit, and thus there are only 16,777,216 possible IV’s
A busy network will repeat IV’s often
By listening to the encrypted traffic and picking out the duplicate IV’s, it is possible to infer what parts of the WEP key are
Enough duplicate IV’s and you can figure out the whole WEP key
ECE Internetwork Security

16. ECE 4112 - Internetwork Security
The Weak IV attack
Some IV’s do not work well with RC4
Using a formula, one can take a weak IV and infer part of the WEP key
Once again, passively monitoring the network for a few hours can be enough time to gather enough weak IV’s to figure out the WEP key
ECE Internetwork Security

17. Taking a look back on WEP
WEP is flawed by a technology weakness, and there is no simple solution to fix it
Increasing key length will only help against a brute force attack (trying to guess the key). The IV is the weakness in this protocol, so increasing key length is pointless
Attacks against WEP are passive and extremely difficult to detect
ECE Internetwork Security

18. Security beyond 802.11 specifications
For a secure wireless network, you MUST go above and beyond the b security measures.
At this point, there are many measures you can take to secure a wireless network. All have their pro’s and con’s, and of course some work better than others
The Goal: a secure network that is easy to deploy and maintain.
ECE Internetwork Security

19. ECE 4112 - Internetwork Security
Hiding the SSID
As stated earlier, the SSID is by default broadcast every few seconds.
Turning it off makes it harder to figure out a wireless connection is there
Reading raw packets will reveal the SSID since even when using WEP, the SSID is in plain text
Increases deployment difficulty
ECE Internetwork Security

20. ECE 4112 - Internetwork Security
MAC address filtering
MAC address filtering works by only allowing specific hardware to connect to the AP
Management on large networks unfeasible
Using a packet sniffer, one can very easily find a valid MAC address and modify their OS to use it, even if the data is encrypted
May be good for small networks
ECE Internetwork Security

21. Counter measures that could have prevented this!
Only allow users to connect to servers on the wired LAN with secure protocols. If that is not an option, use a firewall to block insecure connections to servers on the wired LAN
Use of 802.1X and a secure EAP if possible
If convenient, a VPN would greatly increases security of data
ECE Internetwork Security

22. Things to keep in mind when securing a WLAN
All WLAN should be considered insecure, and thus should be treated that way
Never put a WLAN within the perimeter of your wired LAN’s firewall
Use WEP, it will deter most would be trespassers
Do not leave default WEP key
Implement 802.1X with key rotation every 5 to 10 minutes
Combine security mechanisms.
ECE Internetwork Security

23. Future of wireless security
802.11i is in progress, and addresses security issues in b
802.11i will in essence be a standardized way for b and 802.1X to be coupled, and introduce new ciphers
TKIP cipher should be able to be used on existing hardware with new firmware
New ciphers based on AES encryption will require new hardware
ECE Internetwork Security

24. ECE 4112 - Internetwork Security
Lab Goals
Examine Unencrypted Wireless Traffic
Circumventing MAC Address Filtering
Cracking WEP using AirSnort
ECE Internetwork Security

25. ECE 4112 - Internetwork Security
Network Layout
D-Link Wireless AP
(2).144
WindowsXP2
FTP Server
(2).150
WindowsXP1
FTP Client
(2).100
Evil RedHat Linux 8.0
Sniffer
(2).50
ECE Internetwork Security

26. Unencrypted Wireless Traffic
ECE Internetwork Security

27. ECE 4112 - Internetwork Security
MAC Address Filtering
Use Kismet to find a valid MAC Address
Spoof your MAC address
With no encryption, full access should be granted
ECE Internetwork Security

28. ECE 4112 - Internetwork Security
Cracking WEP
Cracking using AirSnort can take a considerable amount of time, so you will be provided with a nearly complete log file
ECE Internetwork Security

29. Links to the tools used:
Airsnort
Netstumbler
Ethereal
ECE Internetwork Security

30. Papers and Wireless Security Web Pages
Weaknesses in the Key Scheduling Algorithm of RC4
The Unofficial Security Web Page
Wireless Security Blackpaper
The IEEE specifications (includes WEP spec)
Paper on detecting Netstumbler and similar programs
Further reading on upcoming variations
Assorted related crypto algorithms written in ANSI C
ECE Internetwork Security

31. ECE 4112 - Internetwork Security
Acknowledgements
Brian Lee authored most of these slides.
ECE Internetwork Security