In the field of networking, the specialist area of network security consists of the provisions made in an underlying computer networksrtp, policies adopted by the network administrator to protect the network and the network-accessible resources from unauthorized access, and consistent and continuous monitoring and measurement of its effectiveness (or lack) combined together. Security Management for networks is different for all kinds of situations. A small home or an office would only require basic security while large businesses will require high maintenance and advanced software and hardware to prevent malicious attacks from hacking and spamming.

“A network has been defined as any set of interlinking lines resembling a net, a network of roads
an interconnected system, a network of alliances.”

This definition suits our purpose well: a computer network is simply a system of interconnected computers.How they‘re connected is irrelevant, and as we’ll soon see, there are a number of ways to do this. Network security is a level of guarantee that all the machines in a network are working optimally and the users of these machines only possess the rights that were granted to them.

This can include:

  • preventing unauthorized people from acting on the system maliciously
  • preventing users from performing involuntary operations that are capable of harming the system
  •  securing data by anticipating failures
  •  guaranteeing that services are not interrupted

Need for Security of Computer Networks

Security is often viewed as the need to protect one or more aspects of network‘s operation and permitted use (access, behavior, performance, privacy and confidentiality included). Security requirements may be Local or Global in their scope, depending upon the networks or internet work‘s purpose of design and deployment. Criteria for evaluating security solutions include ability to meet the specified needs / requirements, effectiveness of approach across networks, computing resources needed vis-à-vis the value of the protection offered, quality and scalability, availability of monitoring mechanisms, adaptability, flexibility, practicability from sociological or political perspective economic considerations and sustainability. Security Attacks compromises the information-system security. Active attacks involve active attempts on security leading to modification, redirection, blockage or destruction of data, devices or links. Passive attacks involve simply getting access to link or device and consequently data.

Security Threats are those having potential for security violation. Security Mechanism is a mechanism that detects / locates / identifies / prevents / recovers from ―security attacks. Security Service is a service that enhances security, makes use of the security mechanisms. Importance of identification of sources cannot be underestimated. Strategic importance applies to planning, preventing and / or countering whereas other variety of importance is with respect to Sensitivity-analysis and Economic-impact-analysis and pro-active protection.

Elements of Network Security Primary elements of security of any computer network include security provisioning at the Sending Node, Intermediate Forwarding Node, Receiving Node, interconnection links and mechanism of transmission / reception at physical and logical levels. Extraneous factors that these elements may be influenced by may include various kinds of external and internal attacks, unintentional leakages and location of devices involved in communication. Apart from the obvious networking elements, network security is also influenced by the System and Application Software security provisioning or lack of it on individual nodes. Now that an overview of network security has been given to you, now we should move on to various network securities included and we will go in detail of each of them. Firstly let us look into the mobile security.


“Mobile means mobility or which lets you move.”

The term “mobile” implies portability; so, a mobile device, such as a Palm Pilot, is one that easily travels with you. The term also commonly implies that the device has an “always on” connection to the Internet. So we see that the adjective mobile denotes two different scenarios: offline and online. Mobile offline means that you can use the device to run self-contained programs without a live Internet connection.

You can “sync” with a PC to download software, e-mail messages, and other content onto your PDA for portable reading or offline reference. Data collected on the road can be synchronized with a PC once you get back to the office or uploaded whenever an Internet connection is established. The handheld scanners that FedEx drivers use to capture delivery information, such as signature,
are a good example of a mobile but offline device.

When the driver returns to the delivery van, he can sync the handheld scanner with an onboard computer, and the information is uploaded into the FedEx network. In figure given below you can see online and offline mobile scenarios. Mobile online is commonly called wireless. This means that users are connected to the Internet via satellite, cellular, or radio transmitters. (Radio transmitters are the technology behind Wi-Fi networks, which currently are receiving much attention and funding.)

An online device will be “always on” in the presence of any wireless data network – seamlessly connecting to the Internet so it can exchange e-mail and instant messages and retrieve web content. The extremely popular BlackBerry RIM handhelds are capable of all these activities and, notably, allow users to securely access corporate e-mail accounts.

Architecture of Mobile Communication: Each mobile uses a separate, temporary radio channel to talk to the cell site (base station mobile. Channels use a pair of frequencies for communication one frequency, the forward link, for transmitting from the cell site and one frequency, the reverse link, for the call site to receive calls from the users. Radio energy dissipates over distance, so mobiles must stay near the base station to maintain communication. Codec‘s convert an analog speech signal to its digital representation by sampling analog signal at regular time intervals called pulse code modulation. For analog data to be transmitted analog modulation techniques like amplitude modulation and frequency modulation are used. The modulation techniques used for digital signal transmission are amplitude shift keying, frequency shift keying, phase shift keying.

Mobile Communication system

Figure: Mobile Communication


Cell tower: A cell tower is the site of a cellular telephone transmission facility. Wireless coverage is divided into hexagonal-shaped coverage boundaries, with one cell tower covering each region. This hexagonal shape varies depending on the network ̳s geographic coverage.

Base station controller (BSC): A BSC controls a cluster of cell towers. It is responsible for setting up a voice or data call with the mobile terminal and managing handoff without disrupting service when the phone moves from one cell tower boundary to another. A BSC is also commonly called a base station.

Mobile switching center (MSC): An MSC connects all the base stations to pass communications signals and messages to and from subscribers operating on the network. An MSC is connected to a visitor location register (VLR), a home location register (HLR), an authentication center (AuC), and an equipment identity register (EIR).

Visitor location registers (VLR): A VLR records information about mobile devices that have roamed into their network from other networks, that is, out of their home calling area. For example, if a mobile device is registered to operate with a network in New York and it ̳s initiating a call in Boston, the VLR registers details about the mobile and its plan in Boston.

Home location registers (HLR):An HLR keeps track of information about the subscriber. The HLR keeps a record of the last time the mobile cell phone was registered on the network. Mobile devices register with a wireless
network every few seconds to identify their location. This helps to speed call setup when BSCs have to find the mobile device.
Mobile identity number (MIN) and electronic serial number (ESN). All mobile devices used in a wireless network carry these identification numbers. The MIN and ESN are used for verification, authentication, and billing purposes.

Equipment identity register (EIR):An EIR stores and checks the status of MINs and ESNs.

Authentication center (AuC):AnAuC is responsible for authentication and validation of services for each mobile device attempting to use the network.

Operations and maintenance center (OMC):An OMC is connected to the network to provide functions such as billing, network management, customer care, and service provisioning.