1. WIRELESS NETWORKS

2. OBJECTIVES Define terms associated with wireless networks.
Explain strengths and weaknesses of various wireless mediums.
Discuss the hardware necessary to build a wireless network.
Understand the two basic modes of WLAN operation.
Discuss the importance of wireless security.
Explain several methods/tools available to harden wireless networks.

3. Intro to 802.11 What is wireless? Infrared Data Association (IrDA)
Bluetooth
Satellite
Wi-fi

4. IrDA Uses infrared light Very short range
PANs only
Requires a direct line-of-sight (LOS) from sender to receiver
Much more secure than RF transmissions in most cases due to the LOS requirement
2.4 kbit/s to 1 Gbit/s
Newer implementations are very fast—sub-second time to transfer a picture!
Source:
PAN: Personal Area Network

5. Bluetooth
Bluetooth is a wireless technology for short-range (max of 100 meters) PANs
Bluetooth provides a way to connect and exchange information between devices such as mobile phones, laptops, PC’s, printers, digital cameras and video game consoles.
Uses short wavelength radio transmissions
Originally designed to wirelessly replace RS-232 cables
Source: 2. 3.
RS-232: Serial standard. Shown is a Serial cable.

6. Satellite Communication
Expensive!
Time delay
Maybe the only path for data you have
Ship
Remote Locations

7. Intro to 802.11 The “Governing” bodies
Institute of Electrical and Electronics Engineers (IEEE)
Regulate the standards that drive IEEE devices
Federal Communications Commission (FCC)
Regulates and sets rules for numerous radio wave technologies, including WLANs!

8. What is a wireless LAN? Same as wired LAN except:
Different medium used to send data from one node to another.
No wires!
Layer 2 and below is different
Data Link layer
Coordinates access between nodes to a common medium and recovery from errors introduced during travel through the wireless medium.
IEEE
Institute of Electrical and Electronics Engineers
a, b, g, n
Oldest (a) to newest standard (n)
Wi-Fi
Superset of IEEE
Typically--means the same thing as IEEE
Source:

9. Intro to
Standard
Year*
Frequency
Max Data Rate
Security
Backwards
Compatible?
802.11
1997
2.4 GHz
2 Mbps
WEP
N/A
802.11a
1999
5 GHz
54 Mbps
WEP and WPA N
802.11b
11 Mbps
Y** (802.11)
802.11g
2003
Y** (802.11,b)
802.11i
2004
2.4 & 5 GHz
---
WPA2
Y (a, b, g)
802.11n
2009
300+ Mbps
WPA and WPA2
Y**(a, b, g)
Source:
*Year first ratified, as is now known as ( legacy)
**Although each standard is backwards compatible with previous standards, throughput may be limited by the older standard in use

10. Frame
Source:

11. Hardware Station Wireless Network Interface Card (WNIC)
Any wireless device that can be connected to a network
Needs a WNIC to function
Wireless Network Interface Card (WNIC)
Also called a wireless network adapter
Connects your station (computer) to the wireless network
Every computer on a wired network has a NIC as well
Most laptops have NIC’s that are compatible with both IEEE AND Ethernet
Wireless router/access point (AP)
Typically connected via wire to the internet
Connects stations to the internet via some wireless medium

12. Hardware Bridges Used to connect sections of wired Ethernet
Most commonly Point-to-Point
Other varieties exist:
Point-to-Multipoint
Wireless Workgroup Bridge
Clients usually can’t connect with a bridge, but can to a WWGB
Source:

13. Hardware Repeaters Re-transmits signal from the primary AP
Source:

14. Architecture Basic Service Set (BSS)
One access point, along with all the stations that are connected to that access point
Basic Service Set ID (BSSID)
“MAC address of the AP servicing the BSS” (1)
Router/access point broadcasts an SSID (Service Set Identifier)
Name of your wireless LAN
Plain text
When a router/AP advertises its SSID
Stations can “find” or “see” your network when not connected
Can turn SSID advertising on/off at the router/AP
Source: 2.

15. Infrastructure Mode
Internet AP
hub, switch
or router AP
BSS 1
BSS 2

16. Architecture Extended Service Set (ESS)
One or more BSS’s connected together
Common SSID
Two major modes of WLAN operation
Infrastructure
What we’ve described so far (home/office wireless LAN)
One or more router(s)/AP(s) that connect stations to the internet
Ad-hoc
Sometimes called peer-to-peer (P2P)
Stations connect to each other when “in range”
No connection to an AP/router
This station-only BSS, called an IBSS or Independent BSS cannot connect to other BSS’s
Examples:
wireless sensor networks
Group of employees with laptops convene for a meeting; employees link computers in a temporary network for duration of meeting

17. Wireless Security Why is it important?
The accessibility of wireless networks make them juicy/visible targets
Access to a wireless network can lead to:
Access to the nodes on the LAN
Access to the wired network behind the AP that is servicing a given BSS

18. Wireless Security Wireless Security Measures: SSID Cloaking
MAC Filtering
Encryption
VPN
Wireless Intrusion Prevention System (WIPS)
RF Shielding
Many others
Source:

19. Wireless Security Service Set Identifier (SSID) Cloaking
Stops router/AP from advertising network name
Windows clients and Netstumbler will not detect the wireless network
Stations must request to join the WLAN with the correct SSID (like a secret door hidden behind a bookshelf, that only opens when you pull on the right book)
If a cracker doesn’t know your LAN is there, they will not try to break in!

20. Wireless Security Media Access Control (MAC) Filtering
Restricts which clients can link to the AP based on MAC address
Not easy to implement on large networks
Must type all MAC addresses with access into a list stored in the AP/router

21. Wireless Security 802.11 Encryption None WEP40 WEP104/128 WEP+ WPA-PSK
“Weakest to Strongest”*
None
WEP40
WEP104/128
WEP+
WPA-PSK
WPA2-PSK
WPA Enterprise
WPA2 Enterprise
*In the most secured standalone state. In some cases, it is easier to attack WPA-PSK networks than WEP40 networks.
Source:
PSK: Pre-Shared Key

22. Wireless Security Wired Equivalent Privacy (WEP)
Designed as a basic, low tradeoff (throughput vs. security) encryption
Two mainstream flavors
64-bit
128-bit
Not suitable for securing a WLAN segment anymore
Relies on a single shared key among users
24 bit key has a 50% probability of repeating every 5000 packets
Can be broken by sniffing < 10 min of traffic
Takes only a few seconds if you utilize packet injection

23. Wireless Security Wi-fi Protected Access (WPA) Two mainstream flavors
Designed as an upgrade over WEP
48 bit key versus 24 bit key
Sequence Counter Added (so you can’t “replay” data without knowing count)
Actual key is not used for each packet
Derived from actual key
Two mainstream flavors
Pre-Shared Key (PSK)
Ideal for the small office and home user
Strong pass-phrase can make network pretty impenetrable
Enterprise
Requires an external authentication server (i.e. Radius)
Complex setup
Typically only used in large companies/government organizations

24. Wireless Security Wi-fi Protected Access v2 (WPA2)
Common name for the i RSN
Uses Advanced Encryption Standard (AES) instead of RC4 (Rivest Cipher 4)
But still allows for RC4 backwards compatibility
Two mainstream flavors
Pre-Shared Key (PSK)
Enterprise

25. Wireless Security Virtual Private Network (VPN)
Designed to protect switched networks at Layer 3.
Does not protect WLANs at Layer 1 or Layer 2
Fairly secure if “split tunneling” is disabled.
If disabled, the user cannot access the internet through his/her local connection while logged into the VPN
Source:

26. Wireless Security Wireless Intrusion Prevention System (WIPS)
“A network device that monitors the radio spectrum for the presence of unauthorized APs (intrusion detection), and can automatically take countermeasures (intrusion prevention)” (2)
RF Shielding
“Special paint or film (for windows) that attenuates wireless signals” (1)
Source: 1. 2.

27. OBJECTIVES Define terms associated with wireless networks.
Explain strengths and weaknesses of various wireless mediums.
Discuss the hardware necessary to build a wireless network.
Understand the two basic modes of WLAN operation.
Discuss the importance of wireless security.
Explain several methods/tools available to harden wireless networks.