Nokia C111 DATA Security Manual

Data Security

INTRODUCTION

Wireless local area networks are experiencing rapid growth. A continuously
changing business environment requires greater flexibility from people and their
working equipment. Therefore, enterprises of all sizes are starting to realise the
importance of wireless connectivity inside the office premises. At the same time, the
IEEE 802.11 and IEEE 802.11b industry standards for wireless LANs have opened
up new possibilities for implementing wireless LAN solutions. With new
interoperable wireless LAN products on the market, all enterprises and
organisations are able to enjoy the convenience of wireless LANs. Many of these
enterprises handle highly confidential data, and therefore security issues are often
considered to be very important.

A wireless LAN is a flexible data communication system implemented as an
extension to a wired LAN within a building or campus. Using radio frequency (RF)
technology, wireless LANs transmit and receive data over the air, minimising the
need for wired connections. Wireless LAN provides users with mobile access to a
wired LAN in its coverage area. Wireless LAN has recently gained popularity in a
number of vertical markets, including health care, retail, manufacturing,
warehousing, and universities. These industries have profited from the
productivity of using handheld devices and laptop computers to transmit real-time
information to centralised hosts for processing. The demand to use LAN facilities
wherever you are, and to work without complicated installations and cables, is also
increasing in the everyday office environment. Standardisation of wireless LAN
technologies makes it more attractive to extend or replace a part of a traditional
LAN with a wireless solution.

When planning networking architecture, security issues should be carefully
considered and all necessary security measures should be taken to ensure the
confidentiality and integrity of data in both wired and wireless local area networks.
Unlike telecommunication networks, LAN networks with IP traffic and access to
the public Internet do not provide high reliability or guarantees of security.
Without adequate precautions, any LAN, wired or wireless, may be vulnerable and
subject to security risks and problems. For example, network data can be accessed
or even altered by a hostile outsider who wishes to cash in by selling confidential
business information to competitors. In the last couple of years, these risks have
been complicating the full-scale use of wireless LANs containing confidential data,
because users typically have strict requirements and policies for security and data
integrity.

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OVERVIEW OF DATA SECURITY

Security threats

Computer systems and networks face severe security threats, which may cause
serious damage to a system, its services, or its information. A security attack is an
action that compromises the security of information owned by a company, whereas
a security threat is the possibility of execution of such an attack. Some commonly
known threats are denial of service, interception, manipulation, masquerading,
and repudiation.

Denial of service means that a system or network becomes unavailable for
authorised users, or that the communication is interrupted or delayed. This
situation could be caused by overloading a network with illegal packets, for
example. In the case of wireless LAN, it can be caused by deliberate interference to
operating radio frequencies, which disturbs the wireless network.

Interception can mean identity interception, in which the identity of a
communicating party is monitored for the purposes of later misuse, or it can refer
to data interception, in which an unauthorised user monitors user data during a
communication session. This is an attack on confidentiality, and an example
would be where an attacker listens in on the wireless - or wired - medium and
captures the transmitted data.

Manipulation refers to a situation where data is replaced, inserted, or deleted in a
system. This is an attack on data integrity and can be either unintentional (due to a
hardware error) or intentional, where an attacker listens in on data communication
and modifies user data.

Masquerading takes place when an attacker pretends to be an authorised user in
order to gain access to information or to a system. An example of this in a wireless
LAN would be when an unauthorised user tries to gain access to the wireless
network.

Repudiation means that a user denies having done something that may be harmful
for the system or communication. For example, users may deny that they have sent
certain messages or used a wireless LAN system.

Security services and mechanisms

In order to protect against the above security threats, various security services and
mechanisms need to be used. Security services enhance the security of information
system and data transmissions. Security mechanisms, on the other hand, are the
active measures that are used to provide security services. Encipherment is an
example of a mechanism that can be used with different security services.

Authentication is a service that confirms the identity of an entity, such as a user or
a device, or confirms the originality of a transmitted message. Authentication is
typically needed to protect against masquerading and modification. In current
wireless systems, for example, access points need to authenticate wireless devices to
prevent unauthorised access to the network. Closely related to authentication is the
access control service, which limits and controls access to network systems and
applications. Entities must first be identified, or authenticated, before granting
them access to a system.

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Data confidentiality is the protection of transmitted data from interception. In
wireless communications, this could mean that the data transferred between a
wireless device and an access point in the air interface is kept private. Naturally, not
all data is considered confidential, but critical information should not be
transmitted unless security measures have been taken.

Data integrity is an important security service that proves that transmitted data has
not been tampered with. Authenticating the communicating parties is not enough if
the system cannot guarantee that a message has not been altered during
transmission. Data integrity can be used to detect and protect data from being
manipulated.

Non-repudiation prevents an entity from denying something that actually
happened. This usually refers to a situation where an entity has used a service or
transmitted a message, and later claims to not have done so.

SECURITY AND IEEE 802.11

Various security protocols and solutions exist that enable the protection of
transmissions in computer networks. These can also be applied to wireless LANs
where traffic needs to be protected from eavesdroppers. This section introduces the
solutions that can be used to solve security problems in wireless LANs.

The IEEE 802.11 wireless LAN standard was ratified in 1997. The standard was
developed to maximise interoperability between different brands of wireless LAN
products as well as to introduce a variety of performance improvements and
benefits. The IEEE 802.11 standard defines three PHY layer options: FHSS, DSSS,
and IR. DSSS has some benefits compared to the other two PHY layer options.
DSSS has the highest potential data rates (up to 11 Mbit/s), and it provides a greater
coverage area than the FH and IR options. DSSS systems were originally used in
military communication. DSSS-based radio systems are also very robust against
interference.

The existing IEEE 802.11 wireless LAN standard defines two authentication
services:

• Wired equivalent privacy (WEP) based shared key authentication

• Open system authentication (simply announces that a wireless device desires to
associate with another wireless device or access point)

Wired equivalent privacy - WEP

The stations in an IEEE 802.11 wireless LAN can prevent eavesdropping by
implementing the optional WEP algorithm, which is also used in the shared key
authentication scheme. The WEP algorithm utilises the RC4 algorithm with an up
to 128-bit secret key. When the wireless devices in a wireless LAN wish to
communicate using WEP, they must have the same secret key in possession. The
standard does not dictate how the keys are distributed to the wireless devices.

From a cryptographic point of view, the key length and the protection provided by
the algorithm are important, whereas from a systems architecture point of view,
the manner in which the WEP keys are distributed and managed is essential since
security is based on keeping the secret keys unexposed. WEP expects that the shared

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