Wireless Security

Wireless Security

Traditional Security Issues • Integrity • Integrity can refer to either system integrity or data integrity. • Data maintains its integrity if the receiver of the data can verify that the data have not been modified; in addition, no one should be able to substitute fake data.

Confidentiality • Confidentiality refers to data and is provided when only intended recipient(s) can read the data. • Anyone other than the intended recipients either cannot retrieve the data because of access mechanism protections, or other means, such as encryption, protect the data even if they are stolen or intercepted.

Nonrepudiation • Non repudiation is a property of data and means that the sender should not be able to falsely deny (i.e., repudiate) sending the data. • This property is important for electronic commerce because vendors do not want clients to be able to deny that they made purchases and thus must pay for any services or goods they received.

Availability • Availability is a property of systems where a third party with no access should not be able to block legitimate parties from using a resource. • There have been numerous DoS attacks; notable ones include “syn flood,” “smurf,” “ping of death. • The “syn flood” attack creates many “halfopen” Transmission Control Protocol (TCP) connections so that the target computer no longer accepts any new connections. • The “smurf” attack sends an Internet Control Message Protocol (ICMP) packet to a broadcast address resulting in a large number of replies, flooding a local network.

Mobile and Wireless Security Issues • Detectability • One problem associated with wireles communication is detectability. Non mobile users typically do not face this problem. • In some circumstances, the mobile users do not want their wireless system to be detected, and this is part of the reason they are mobile. • Even if strong encryption is used and the data cannot be deciphered, the mere presence of the signal can put the user at risk. • If the enemy can detect the signal and locate its position, the device can be jammed by local radio frequency (RF) interference, the soldier can be captured by troops sent to that location, or he can be killed by remote weapons that target that location (e.g., bombs, artillery shells, etc.).

Resource depletion/exhaustion • Another problem unique to mobile systems is that the resources often are very limited. • To keep the mobile unit small and lightweight, the designers often make compromises. The CPU speed may be an order of magnitude or more slower than that of conventional desktop machines. • The network bandwidth may be similarly limited. • The biggest constraint on these systems is the battery. Often these systems run on internal batteries because AC power is not available owing to location (e.g., being outside) or because they are moving continually and would require a very long and impractical extension cord. • This leaves these devices open to resource-depletion and exhaustion attacks.

Physical intercept problems • One major difference between wired and wireless systems is the ease of physical intercept of the signal. • In wireless systems, the signal is broadcast through the air, where any receiver can intercept it. • In general, the approaches to mitigate this problem involve directional antennas, low-power transmissions, and frequency-hopping/spread-spectrum technology at the physical layer and encryption techniques at higher layers.

Theft of service • A final problem we will discuss is theft of service. While this problem has plagued computer systems seemingly forever, wireless systems are particularly prone to it. Normally, a system requires a user name and password to gain access to it.

War driving/walking/chalking • There is a whole class of war terms that originate from the term war dialing. Back in the 1980s, before the widespread popularity of the Internet, hackers and crackers would search for phone numbers with modems attached to them by using programs they would dial every number in an exchange and listen for the modem tones.

War walking and similar variants (e.g., war flying) reflect different modes of transportation. In this case, the term refers to scanning for wireless networks by using a lightweight computer (personal digital assistant or palmtop or small laptop) and walking around an area

War driving is the wireless equivalent of war dialing. The technique involves taking a computer with a wireless card running some detection software [netstumbler, kismet, airsnort, wardriving] and optionally a Global Positioning System (GPS) and driving around a city. The softwar detects the presence of wireless networks, and the GPS gives the location for later reference.

One other variant that started to become popular in 2002 is war chalking, which is the practice of marking the presence of wireless networks with chalk either on sidewalks or on the sides of buildings. • The three symbols shown in Figure represent an open network, a closed network, and a Wired Equivalent Privacy (WEP) password protected network.

Mobility • One of the essential characteristics of mobile computing is that the locations of the nodes change. • Mobility provides many freedoms, but it also increases several security risks. Dynamically changing routes, potential lack of a trusted path, disconnected operation, and power limitations all increase the security risks.

Problems in Ad Hoc Networks • ad hoc networks must propagate messages from one wireless station to the next until they reach the destination or a border (typically the Internet). • Ad hoc networks form on the fly, without a fixed infrastructure. • Data in ad hoc networks typically pass through several other ad hoc nodes. Typically, there is no guarantee as to the identity of these intermediate nodes, so “man in the middle” attacks can be used to copy or corrupt data in transit. • Because nodes are mobile, the route between any two nodes is dynamic, even if the endpoints are stationary.

A route between two nodes can be disabled by two malicious nodes that share a common segment along the route. In an ad hoc network, key routing nodes can be disabled via a resource-exhaustion attack in this manner. • ARP Spoofing • ARP cache posioning

Prekeying • One problem when using encryption or authentication is key management, which involves creating, sharing, storing, and revoking encryption keys. • Public key encryption is one way to avoid needing a key exchange. If a symmetric key algorithm is used, then the two endpoints must agree on a key, either via a key-exchange protocol, such as IKE or DiffieHellman, [IKE, Diffie-Hellman or decide on a key a priority.

Reconfiguring • Reconfiguring poses another problem in ad hoc networking. • Because ad hoc networks are, by nature, dynamic, as nodes move they go out of radio contact with some nodes and come into contact with other nodes. • The network topology itself changes over time. This means that a previous route from node X to node Y may no longer work. • Ad hoc routing algorithms must be able to reconfigure the underlying view of the network dynamically.

Hostile environment • The mobile environment is often more hostile than the non mobile one. • In a non-mobile environment, physical boundaries and barriers have more meaning and change less frequently. In a mobile environment, eavesdropping is easier. • Physical locations often are not secured, e.g., coffee shops and airports, and nodes go in and out of contact regularly

Additional Issues: Commerce • Electronic commerce is a prime application of and domain for mobile computing. • The vast commercial potential for this drives the development and deployment of the technology, making common place mobile computing a reality. • Generally, security is at odds with convenience, and in a commercial market, convenience takes precedence

Liability • Currently, liability issues relating to computer security are still being determined. • Not only do computers contain potentially useful information, such as customer credit card numbers, but machines on the Internet also can be used as spring boards to launch attacks on other Internet computers. • Some businesses have been sued because of their lack of “due diligence” by not installing patches, antivirus software, and similar protection.

Fear, uncertainty, and doubt • Another aspect of electronic commerce is the “intangibles” from public perceptions. • Companies that suffer from break-ins often are reluctant to report them because of the fear that such a report will hurt their reputations. • Often, the costs of these break-ins simply are included as the cost of doing business.

Additional Types of Attacks • “Man in the middle” attacks • Replay attacks • Buffer-overflow attacks

Wireless Security