Know Computer Security

Computer Security

Now-a-days computers are becoming a reliable source to create,store and manage critical information.It is also crucial that users take measures to protect their computers and data from loss,damage,and misuse.For example,a company must ensure that information,such as credit records,employee and customer data and purchase information are secure and confidential.
Computer security risk is a term known for any event or action that could be harmful for a computer hardware,software,data information or processing capability.Some breaches to computer security are accidental while others are planned.Any illegal act involving a computer is generally referred to as a computer crime.The term cybercrime refers to online or internet-based illegal acts.
The following sections describes some of the more common computer security risks and safeguards,you can take to minimize or prevent their consequences.
Computer Viruses
Virus is a potentially damaging program in a computer,which negatively effects or infects your computer without your knowledge and alters the working of the computer.More specifically,a computer virus is a segment of program code from some outside source that implants itself in a computer.Once a virus is in your computer,your files and operating system may be damaged.
The increased use of networks,the internet and email has accelerated the spread of computer viruses.With these technologies,computer users easily can share files and any related viruses.Viruses are activated on your computer in three basic ways:
(1)Opening an infected file
(2)Running an infected program
(3)Booting the computer with an infected floppy disk in the disk drive.
The most common way of virus in a computer is through the attachment in an email.Before you open or execute any email attachment,you should ensure that the email message is from a trusted source.A trusted source is a company or person you believe will not send you a virus infected file knowingly.You should immediately delete any email received from an unknown source without opening or executing the attachment.Thus you can protect your computer against viruses if you follow the precautionary measures.
Viruses in computer are not generated accidentally but are programmed intentionally by a programmer known as a virus author.Some virus authors find writing viruses a challenge.Others write them to cause destruction.Writing a virus program usually requires significant programming skills.Some viruses are harmless ranksthat simply freeze a computer temporarily or display sounds or messages.The music bug virus,example,instructs the computer to play a few chords of music.Other viruses destroy or corrupt data stored on the hard disk of the infected computer.If your computer acts differently from usual,it may be infected with a virus.
Today,viruses pose as serious threat to the safety of a computer.Currently,more than million known virus programs exist with an estimated 6 new virus programs discovered each day.
Though there are numerous variations,3 main virus types known to exist are,boot sector,file and macro.
A boot sector virus also known as a system virus,executes when a computer boots up because it resides in the boot sector of a floppy disk or the master boot record of a hard disk.When you leave a floppy disk in the floppy disk drive and boot up the computer,the computer attempts to execute the boot sector on the disk in drive A.The hard disk of a computer can be infected by any virus on the floppy disk’s boot sector even if the disk is not the boot disk.

Our Frog family Amphibia

Amphibia are cold blooded animals.

Poikelotherms- cold blooded
Home other swarm blooded.

It may be defined as a class of those animals which are cold blooded vertebrates amphibious in habit having tetrapodous limbs or pentadactyle pattern and require presence of water for breathing purpose.Amphibia have got an intermediate position between fishes and reptiles. They resemble in general pattern of their body with fishes and to some extent in anatomical pattern of body they are more reptilian. In development they are fish like and exhibit many important fish characters in larval forms.They possess some important characters which are mentioned below-
1)In animal kingdom amphibians are placed between fish and reptiles. They include frogs,toads,salamanders, Gymnophions(Apoda-order limbless amphibians or Ceacelians).They are amphibious in habit i. e. they may live on land as well as in water.They have 2 pairs of pentadactyle limbs.

2)They are cold blooded animals. Their skin is smooth or rough,moist, glandular and naked without any scales except in Gymnophiona.

3)Eyes with movable eyelids.

4)Nostrils paired and connected to mouth cavity.

5)Skull with occipital condyles to articulate with atlas.

6)Teeth present.

7)Heart 3 chambered,RBCs nucleated and oval.

8)Respiration by gills,lungs,skin and by buccal cavity.

9)Aotic arches symmetrical.

10)Kidney mesonephric provided with permanent nephrostoma.

11)Cloaca present which receives duct from reproductive system, excretory system and opening of digestive system.

12)Brain with 10 pairs of cranial nerves.

13)Eggs with gelatinous covering usually laid in water.

14)Larva pass through aquatic stage before metamorphosis.

15)They reveal some parental care.


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Let us know Computer Networkings that are behind the Internet(an update)

Computer network means a collection of autonomous computers interconnected by a single technology.
The internet is a network of networks & the web is a distributed system that runs on top of the internet.

Examples of Networks-
1.Communication
2.Transportation
3.Social
4.Biological
5.Utilities

Components of a network-

• Server                           

1.Dedicated Server
2.Non Dedicated Server

Dedicated Server
We cannot use dedicated servers as a workstation & they are entirely dedicated to their connected workstations. Users access shared directories & resources on dedicated server.Eg. Novel NetWare.

Non dedicated Server
The machine used as a server can also operate as a workstation.

• Workstation

When a computer is connected to a network, it becomes a node on the network & is called a workstation or client.

• Network Interface Card(NIC)

Each computer attached to a network requires a network interface card(NIC) that supports a specific networking scheme such as Ethernet, ArcNet or Token Ring.

• Cabling System

Shared Resources & Peripherals

Network Fundamentals

1.

Local Area Network(LAN)

LAN

a)single building LAN

b)Multiple building LAN

LAN are privately owned networks within a single building or campus of up to a few kilometers in size.

LANs are distinguished from other kinds of networks by 3 characteristics

1)their size

2)their transmission technology

3)their topology

1.LANs are restricted size,which means that the worst-case transmission time is bounded.

2.LANs may use a transmission technology consisting of a cable to which all the machines are attached like the telephone company. Traditional LANs run at speed of 10 Mbps to 100 Mbps,have low delay(microseconds or nanoseconds) & make very few errors.Newer LANs operate at up to 10 Gbps.

3.Topologies for broadcast LANs are bus and ring.

Bus network

In a bus network, at any instant at most 1 machine is the master & is allowed to transmit. All other machines are required to refrain from sending. An arbitration mechanism is needed to resolve conflicts when 2 or more machines want to transmit simultaneously.

IEEE 802.3,popularly called Ethernet is a bus based broadcast network with decentralized control, usually operating at 10Mbps to 10Gbps.


Advantages of bus n/w

1)Short cable length & simple wiring layout because there is a single common data path connecting all nodes.

2)Resilient Architecture
Simplicity in architecture that makes it very reliable from a h/w point of view.

3)Easy to Extend
Additional node can be connected at any point along its length.

Disadvantage
1)Fault diagnosis is difficult
Control of n/w is not centralized. This means that detection of a fault may be performed from many points in the n/w.

2)Fault isolation is difficult
In case where the fault is in the n/w medium itself,an entire segment of the bus must be disconnected.

3)Repeater configuration
When a bus n/w has its backbone extended using repeaters,reconfiguration may be necessary.


Ring

In a ring n/w (loop n/w),several devices or computers are connected to each other in a closed loop by a single communication cable. Here data must travel around the ring to each station in turn until they arrive at the station.A ring can be unidirectional or bidirectional.

    Broadcast n/w can be further divided into static & dynamic, depending on how the channel is allocated.

   Static allocation uses round robin algorithm, allowing each machine to broadcast only when its time slot comes up.

Dynamic allocation method for a common channel are either centralized-there is eg. a bus arbitration unit,which determines who goes next or decentralized -there is no central entity, each machine must decide for itself whether to transmit.

Advantages of Ring n/w

1)Short cable length-A ring topology, is comparable to that of bus & is small relative to that of star.Less connection will be needed,which will in turn increase n/w reliability.

2)No wiring closet space required:since there is only 1 cable connecting each node.

3)Suitable for optical fibre:because traffic on a ring travel in 1 direction.


Disadvantage of Ring n/w

1)Node failure causes n/w failure. If 1node fails to pass through itself,entire n/w has failed & no traffic can flow until the defective node has been removed from the ring.

2)Difficult to diagnose fault:The fault if 1 node will affect all others.

3)N/w reconfiguration is difficult: For a very big ring n/w it is not possible to shut down a small section of a ring.Reconfiguration will have to be done.


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