Week 9

Venue : BK7, Building FTMK.
Date : 14 - 10 -2009
Time : 9.00 a.m. – 10.50 a.m.

Time flies, it’s week number 9! Once again, I would like to remind myself that this month is a critical month for me, so please do not play too much, concentrate to projects and assignments although it is quite tiring sometimes, after this I can play as much possible as I can. So, the lecture for this week was about two of the hottest topic in the field of networking, Wireless Security and Firewall.
Wireless connection has becoming very important because it is very convenient as compared to wired connection. For laptop, just switch on the wireless button then one can connect to the available access point easily. However, one of the weaknesses for wireless connection is that it is very easy to be attacked by others.
The first part of lecture today was basically some sort of revision which we have studied in networking subjects in the previous few semesters. There are two types of wireless mode; they are infrastructure mode and ad-hoc mode. There are two categories of infrastructure mode:

1. Basic Service Set (BSS) – All workstations are connected to one access point.
2. Extended Service Set – Two or more BSSs connect together to form a single subnet.

Now, for ad-hoc mode or sometimes known as peer-to-peer, are independent BSS. It means that the wireless workstations are connected together without connecting to the access point first. After knowing how actually a wireless network works, Mr. Zaki then continue the lecture which is more to the security part of the wireless network. There are three basic security services defined by IEEE for WLAN:

1. Authentication – to provide a security service for verification the identity of communicating client stations.
2. Integrity – to ensure that messages are not modified in transit between the wireless clients and the access point in an active attack.
3. Confidentiality – to provide “privacy achieved by a wired network”
   

Wireless network can be categorised into four types, they are 802.11a, 802.11b, 802.11g and 802.11n. The two security services provided in 802.11b are Authentication (Shared Key Authentication) and Encryption (Wired Equivalence Privacy). Based on what I have understood, the encryption is done by a mechanism called RC4. It is a symmetric key encryption which applying RSA encryption algorithm. The three processes for WEP sending are:

1. Compute Integrity Check Vector (ICV).
2. Encrypt plaintext via RC4.
3. Transmit the ciphertext.
   

The processes are reversed when the ciphertext in order to get the plaintext. There are several WEP safeguards such as shared secret key required, messages are encrypted and messages have checksum. The passive attack happens when attacker collects all traffic or attacker collect two messages (Encrypted with same key and same IV and statistical attack to reveal plaintext). On the other hand, active attack could happen if attacker knows the pair of complement plaintext and ciphertext or through bitflipping method. Although some vendors limited WEP keys, it also can be brute forced in several minutes. The ways to do brute force key attack are:

• Capture ciphertext.
• Search all 240 possible secret keys.
• Find which key decrypts ciphertext to plaintext.

The 802.11 safeguards are as follow:

• Security Policy and Architecture Design
• Treat it as untrusted LAN
• Discover unauthorized use
• Access point audits
• Station protection
• Access point location
• Antenna design

The problem of WEP has been fixed with the replacement of Wi-Fi Protected Access (WPA). No matter how good it was fixed, it still has its weaknesses. The two practical attacks of WPA are dictionary attack on pre-shared key mode and denial of attack.
The lecture then continued with a new chapter called firewall. The capabilities of firewall are:

• defines a single choke point that keeps unauthorized users out of the protected network
• provides a location for monitoring security events
• convenient platform for some Internet functions such as NAT, usage monitoring, IPSEC VPNs

The limitations of firewall are:

• cannot protect against attacks bypassing firewall
• may not protect fully against internal threat
• improperly secure wireless LAN may be accessed from outside the org
• laptop, PDA, portable storage device infected outside then used inside
  

Basically, there are four types of firewall; they are packet filtering firewall, stateful inspection firewall, application-level gateway (application proxy) and circuit-level gateway. Besides that, throughout the lecture I have learnt about the firewall basing. The three types of firewall basing are bastion host, host-based firewall and personal firewall. The last topic for today lecture was about firewall locations. The diagram below shows how actually the firewall is placed: