Security Issues of IEEE 802.11b Wireless Local Area Networks Issues | Analysis | Suggestions | Solutions | Adaptations Seminar on Security Issues of 802.11b presented on 21-10-2008 by Sreekanth G S, 274, R7, Computer Science, Sree Chitra Thirunal College of Engineering
Local Area Networks need not scale only up to a building or a particular location. Present scenarios represent Local Area Networks connecting offices across the continents using methods such as VPN (Virtual Private Network).
99% of the world’s Wi-Fi network issues are caused by interference and most of them from cordless telephones. This issue is termed as Wi-Fi band exploitation and device makers consortium has repeatedly requested IEEE to issue a new freq. band.
Wireless Local Area Network
Released – October 1999
Frequency band – 2.4GHz
Data rate – 4.5 Mbit/s (Typical)
Data rate – 11 Mbit/s (Maximum)
Range - ~38m (Indoor)
802.11b devices suffer interference from other products operating in the 2.4 GHz band. Devices operating in the 2.4 GHz range include: microwave ovens, Bluetooth devices, baby monitors and cordless telephones.
Wi-Fi is not an easy word to wireless deployment of LAN or WLAN. Any solution which addresses all or some of the above mentioned seven security problems need not be an ideal solution to the deployment problems faced by most of the companies.
Any Wi-Fi Router (Example: Linksys WRT54GL) can act as a Wireless AP.
AP login with Credentials can make Client login without credentials.
Management staff “can” go rogue….
2. “Rogue” Access Points
Easy access to wireless LANs is coupled with easy deployment.
Any user can run to a nearby computer store, purchase an access point, and connect it to the corporate network without authorization.
End users are not security experts, and may not be aware of the risks posed by wireless LANs.
Tools like NetStumbler allow network administrators to wander their building looking for unauthorized access points, but it is expensive to devote time to wandering the building looking for new access points.
Nearly all of the access points running with default configurations have not activated WEP (Wired Equivalent Privacy) or have a default key used by all the vendor's products out of the box. Without WEP, network access is usually there for the taking.
If you have deployed a VPN to protect the network from wireless clients, it probably has strong authentication capabilities already built-in.
For corporate users extending wired networks, access to wireless networks must be as tightly controlled. Strong authentication is a must before granting access to the n/w.
In cryptography, the man-in-the-middle attack is a form of active eavesdropping in which the attacker makes independent connections with the victims, relays messages between them, making them believe that they are talking directly to each other over a private connection when in fact the entire conversation is controlled by the attacker.
5. MAC Spoofing and Session Hijacking
802.11 networks do not authenticate frames.
Attackers can use spoofed frames to redirect traffic and corrupt ARP tables.
Access points are identified by their broadcasts of Beacon frames.
You must deploy a cryptographic protocol on top of 802.11 to protect against hijacking.
Attackers can, however, easily pretend to be an access point because nothing in 802.11 requires an access point to prove it really is an access point. (Man-in-the-Middle Attack)
Many networks have a hard outer shell composed of perimeter security devices that are carefully configured and meticulously monitored. Inside the shell, though, is a soft, vulnerable (and tasty?) center.
7. Higher Level Attacks
Once an attacker gains access to a wireless network, it can serve as a launch point for attacks on other systems.
Wireless LANs can be deployed quickly if they are directly connected to the vulnerable backbone, but that exposes the network to attack.
The solution is straightforward in theory: treat the wireless network as something outside the security perimeter, but with special access to the inside of the network.
A pseudorandom process is a process that appears random but is not.
RC4 generates a pseudorandom stream of bits (a keystream) which, for encryption, is combined with the plaintext using bit-wise exclusive-or; decryption is performed the same way (since exclusive-or is a symmetric operation). To generate the keystream, the cipher makes use of a secret internal state which consists of two parts:
A permutation of all 256 possible bytes (denoted "S" below).
Two 8-bit index-pointers (denoted "i" and "j").
The permutation is initialized with a variable length key, typically between 40 and 256 bits, using the key-scheduling algorithm (KSA). Once this has been completed, the stream of bits is generated using the pseudo-random generation algorithm (PRGA).
Pseudorandom sequences typically exhibit statistical randomness while being generated by an entirely deterministic causal process. Such a process is easier to produce than a genuine random one, and has the benefit that it can be used again and again to produce exactly the same numbers, useful for testing and fixing software.
RC4 Algorithm (contd…) The key-scheduling algorithm (KSA) The key-scheduling algorithm is used to initialize the permutation in the array "S". "keylength" is defined as the number of bytes in the key and can be in the range 1 ≤ keylength ≤ 256, corresponding to a key length of 40 – 128 bits. First, the array "S" is initialized to the identity permutation. S is then processed for 256 iterations. for i from 0 to 255 S[i] := i endfor j := 0 for i from 0 to 255 j := (j + S[i] + key[i mod keylength]) mod 256 Swap (S[i],S[j]) endfor
For such applications as cryptography, the use of pseudorandom number generators is insecure. When random values are required , the goal is to make a message as hard to crack as possible, by eliminating or obscuring the parameters used to encrypt the message from the message itself or from the context in which it is carried.
RC4 Algorithm (contd…) The pseudo-random generation algorithm (PRGA) For as many iterations as are needed, the PRGA modifies the state and outputs a byte of the keystream. In each iteration, the PRGA increments i , adds the value of S pointed to by i to j , exchanges the values of S[ i ] and S[ j ], and then outputs the value of S at the location S[i] + S[j] (modulo 256). Each value of S is swapped at least once every 256 iterations. i := 0 j := 0 while GeneratingOutput: i := (i + 1) mod 256 j := (j + S[i]) mod 256 Swap(S[i],S[j]) Output S[(S[i] + S[j]) mod 256] ^ input[i] endwhile
Seven Security Problems – O’Reilly Media - http://www.oreillynet.com/pub/a/wireless/2002/05/24/wlan.html?page=1
Based On: Security issues of the IEEE 802.11b wireless LAN Boland, H. Mousavi, H. Carleton University, Ottawa, Ont., Canada IEEE Canadian Conference on Electrical and Computer Engineering, 2-5 May 2004