Posts Tagged "Viruses Computer"

An Over View Of Computer Viruses

Computer security is a vitally important issue in today’s society, a lot of the most critical aspects of our lives require computers, and keeping those computers secure is critical. The popularity of the Internet and the amount of time we spend making use of it has made it very simple to spread computer viruses.

Computer viruses have become such a problem that they are now frequently mentioned in both the newspapers television news bulletins as well as in the online media. It is absolutely critical that you take steps to protect yourself against viruses, and you must be really vigilant if you spend a lot of time online.

Virus can be transmitted through e-mail, or a file you download even if you do not install it, but they can also be present in the files on a floppy disk especially if it is being passed from friend to friend. Lots of computers get infected every day, and if you do not take precautions yours may be next, you may lose all of your data on your machine. Once gone, it will be irretrievable unless of course you had the good sense to take a regular back up!

A computer virus is a small program that has the ability to duplicate itself, just like a real virus hence the name, also just like a biological virus it must have a host to exist. The virus payload, the end product of the computer virus, can be something harmless it can be as simple as displaying a message, or something very serious it could fully reformat your hard drive. Recent computer virus attacks have resulted in major disruption to both home computers and the networks of governments and multi national companies.

The advance of the Internet has been the most essential issue in the increase of computer viruses. Originally viruses were spread when people swapped disks with their friends, by its very nature this tended to restrict the spread of the computer virus but today most people do not tend to use external media like disks to store data in the same way, This has resulted, most viruses being spread via the use of e-mail and file sharing on the Internet. All that is required is for you to open an e-mail attachment or download a dangerous program and this can give your computer a virus. There are by now, about fifty thousand viruses in existence, but there are several hundred new threats produced each month.

There are a number of motives that encourage people to write computer viruses. The earliest virus programs were by and large written as pranks or experiments. However as some programmers began to learn their way about systems and the Internet, they wrote viruses just to see what they can do with them. For example, a programmer might write a computer virus code just to see how far it would spread. Unfortunately it did not stop there, other more malicious individuals, have far more hostile intentions and they took great delight writing computer viruses to harm websites or damage people’s computers.

An additional reason a computer virus gets produced is to blackmail large corporations with the threat of setting off a loss of data on their systems. There have been lots of viruses written for revenge. Employees who are about to lose their jobs can sometimes leave viruses behind on the company system to do damage to their former employer’s ability to do business.

Also lots of viruses are written for profit. The computer viruses may be used to send e-mail spam (so the original sender is disguised), causing your computer to serve as a host to illegal data, or engage in other illegal activities. Also, viruses can be used to spy on users, display pop-ups while the user is not on the internet, and acquire user data like bank accounts or credit card numbers.

Viruses tend to fall into two major types, Worms or Trojan horses, but just to complicate things Trojan horses, can be a type of worm.

A Computer Worm is a self replicating program, the first worm to gain wide attention was the Morris Worm this infected a large number of computers and earned its writer 400 hours of community service and over $10000 in fines!

Trojan horses as the name implies are hidden viruses. This helps the program to get installed in the first place. They then quietly run in the background, while disseminating its malicious code. This code can do any amount of things. It can begin right away or it may simply install a program that won’t start for sometime. Once it does start, it can delete all of the files on the computer or it can infect the computer and try to infect other computers on the network.

There are a number of ways viruses are delivered, and as a Trojan horse is the most common. It generally comes with other pieces of software that a user might find interesting. This software is usually shared through a file-sharing network or downloadable off of the Internet. Once the user installs the software, the virus also gets installed.

It is vital that you cover yourself against viruses, this can done very simply by installing a good anti-virus program and keeping it up to date. There are both free and expensive software applications around that can be set to self-update to protect from viruses.

You can also help defend yourself by being cautious where you download files from; only use a reputable well-known source. You should also not to open any e-mail attachments unless you know the sender. Making these safety precautions will help to protect you from computer.

Roger Overanout

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Computer Viruses:-

Computer Viruses:-

 

The world of computers and information technology is going through an era of an electronic terrorism, in the form of the computer virus. It is a problem that is potentially so dangerous that it threatens the proper functioning of the virus system in today’s information age.
The virus whether biological or electronic is an information disorder. Biological viruses are tiny genetic codes DNA or RNA that take over the machinery of a living cell and are capable of marking thousand of replicas of the original virus. Like its biological counterpart, a computer virus carries in it an instructional code that makes copies of itself.
Computer viruses are computer programs which are a collection of coded instructions. The basic difference between a normal program and virus is that viruses are self replicating; they have the capacity of executing themselves without being asked for. The ‘Computer virus’ is a very broad term in itself and includes not only viruses, but also worms and Trojans.

 

Classification of Computer viruses:-

 

Viruses are classified on the basic of their mode of existence and there are three categories of viruses.

 

1. BOOT  Infector:-
2. SYSTEM  Infector:
3. GENERAL EXECUTABLE PROGRAM   Infectors:-

 

BOOT Infectors:-
As the name suggests, they are characterized by the fact that they are physically reside in the boot sector [0] sector of the disk. A system infected by such a virus will have the virus residing in a particular area of the disk rather then in a program file. These viruses get loaded soon after the Power Of Self Test and control the system and remains in control at all times. They some times have the capacity to trap soft booting (CTRL ALT DEL) and remain in control even if the system is booted from a non infected floppy, thereby contaminating the clean floppy.

 

SYSTEM Infectors:-
The second category of virus deals with components of the system itself. All machines without execution require an operating system in order to create an environment in which the operator works. In MS-DOS, COMMAND.COM contains all the internal commands. If no such command file exists, commands such as COPY, DIR etc. are not loaded into the memory when the machine is booted. The system infectors attach themselves to a file such as COMMAND.COM or other memory resident files and manipulate these files.

 

GENERAL EXECUTABLE PROGRAM Infectors:-
From the infection point of view, these are most dangerous and devastating of the three classes of viruses. They attach themselves to program files and can spread to almost any executable program in any system. These viruses change the original program instructions into a “jump” to its own code and follow that code with a return to the original program. As a result, whenever the program is executed, the virus gets loaded and executed first and then allows the original program to process. It remains memory resident and infects each and every program that is loaded for execution.

 

Types of Viruses:-

 

Worms:-
A worm is software that uses computer networks and security holes to replicate, or affect other programs. A copy of the worm passes through the network to another machine that has a specific security hole. It then copies itself to the new machine, and then starts replicating from there.

 

Macros:-
Macro viruses’ use commands-called macros-embedded in the other software applications to infect and spread to other files used by that software. For example, Microsoft Word and Excel have macros, and macro viruses can spread by exploiting these commands.

 

Boot Sector viruses:-
Boot sector viruses are older types of virus and are not so common today. They used to infect computers startup programs, so that the virus would become active as soon as the computer started up.

 

Trojan Horses:-
Trojan Horses are programs that claim to perform a particular function but which in fact do something different. For example, they could infect your computer with a virus or erase your files.

 

Backdoor Trojans:-
Backdoor Trojans are programs that allow other computer users to remotely control your computer via a local area network or the internet.

 

Resident Viruses:-
These types of virus hides permanently in the RAM memory. From here it can control and intercept all of the operations carried out by the system corrupting files and programs that are opened, closed, copied etc.

 

Direct Action Viruses:-
When a specific condition is met (such as the execution of the virus) these virus will go into action and infect files in the directory or folder that it in and others as well.

 

Overwrite Viruses:-
These types of viruses are characterized by the fact that it deletes the information contained in the files that it infects, rendering them particularly or totally useless once they have been infected.

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