Facts And Issues Of Viruses Computer Science Essay

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In business nowadays, people cannot escape from using technology to involve in their daily lives. Not only for personal use, technology however also plays an important role on how to run a business. For some department they set up the internet by using LAN (Local Area Network) in order to share documents or files within their organization. Besides, if they do not have a sound knowledge about LAN security, the computers connected to the LAN can be at high risk getting infected by countless viruses. Therefore, this assignment will discuss to the very detail of some typical viruses; how it spreads and some of the ways to prevent computer or software from getting infected by viruses.

Chapter 2

Facts/issues of viruses

2.1 Computer viruses

Viruses in computer is a program or programming code that is loaded onto the computer without the awareness and runs against the requirements replicates itself by being copied or initiating the other programs or applications, computer boot sector, document or file. All kind of viruses are named, and the normal virus which can copy of itself repeat and repeat again is relatively simply to produce. Generally, there are three main types of viruses as following:

File infectors.

Some documents or files are infected from the attached program file that the user often double-clicks on it for example COM or EXE files. Similarly, in some case computer may get infected due to the requested program like SYS, OVL, PRG, and MNU files. Whenever the application or program being loaded, the virus which hides itself on the program also loaded. Another way that virus can infect a computer is through file attachment from an email.

System or boot-record infectors.

This kind of virus can be infecting through code found in some disk area system. The virus hides itself on DOS boot sector of diskettes or the hard disks Master Boot Record. Generally, when the operating system is working, files on the diskette can be read without triggering the boot disk virus. However, if we leave the diskette in the drive and shut down the computer or load the operating system gain, the computer will boot the disk virus, load it, and make it temporarily impossible to use the hard disk.

Macro viruses.

Macro viruses are one the most common viruses’ type and they tend to create the least damage. Macro viruses infect Microsoft Word application and typically insert undesired words or phrases. Since Microsoft Word and Excel are also existed for Mac OS, it can transmit to Macintosh computers as well. Even though this kind of virus is not able to create any harm through email, it can take advantage of the Microsoft Outlook COM interface.

Besides that, some previous versions of Microsoft Word consent to macros to copy themselves with additional blank lines. If two macro viruses at the same time infect a document, the grouping of the two, and does self-replicating, it can appear as a "mating" of the two and would likely be detected as a virus unique.

2.2 Various ways viruses can transmits

Viruses can be spread as attachments file to an e-mail message, downloaded file, or be introduced on a diskette or CD. The basis of the e-mail note, file download, or diskettes is normally ignorant that it includes a virus. Some viruses cause the effect as soon as their code is executed; other viruses lie dormant until circumstances cause their code to be executed by the computer.

Computer viruses can be disguised as attachments of funny images, greeting cards, or audio and video files such "Happy Birthday, Ludwig!" and some can be pretty dangerous, damaging data or causing your hard disk to require reformatting. A virus that replicates itself by resending itself as an e-mail attachment or as part of a network message is known as a worm.

A virus may also send a web address link as an instant message to all the contacts on an infected machine. If the recipient opens a link to access a website, the virus hosted at the site may have ability to infect o computer or others, and continue propagating.

2.3 The areas of infection

Before computer networks became widespread, the majority of viruses infect on removable media and mainly floppy disks. In today of the desktop computer, various users regularly exchanged information and programs on floppies. Thus some viruses tend to spread on programs stored on these disks, while others installed themselves into the disk boot sector.

The viruses would be run when the user booted the computer from the disk, usually inadvertently. Desktop computers of the era would try to boot at the beginning from a floppy if one had been left in the drive. Until floppy disks drop out of use, this had been the most successful and common infection strategy and boot sector viruses were in the wild for many years.

Chapter 3

The preventive measures against viruses

Numerous of users set up anti-virus software which able to discover and remove identified viruses after a computer downloads or runs the certain programs or applications. In the same way, many users also use firewall software in order to prevent their computer from being infected by viruses. Nevertheless, there are many methods that can detect viruses and prevent computer from being infected.

3.1 Anti-viruses

Use virus signature

The first general method of virus detection is to use the register of virus signature definitions. Using virus signature to investigate the content of the memory in computer such as RAM, boot sectors and the files stored on fixed or removable drive such as hard drive, floppy drive. Yet using this specific method, the users have to update the last virus definition regularly to patch security holes. Anti-virus software also needs to be updated in order to prevent the latest threats.

Use heuristic

The second method that is widely used to discover viruses, based on their common behaviors, is “Heuristic” algorithm. This method comes in very useful as it can notice some viruses that anti-virus security firms have not been able to generate a signature for.

3.2 Use fire wall

Fire wall is a device or set of tools which can be implemented in either hardware or software, or a mixture of both. Firewalls are regularly used to avoid unauthorized Internet users from accessing private networks connected to the Internet, especially intranets. The firewall examines all messages that enter or leave the internet. It examines and blocks those that do not meet the specified security criteria. There are several types of firewall techniques:

Packet filter: This filter inspects each packet passing through the network and accepts or rejects it based on user-defined rules.

Application gateway: What this gate way does was to apply some useful security mechanisms to specific applications.

Circuit-level gateway: This is to apply security mechanisms when a TCP or UDP connection is established.

Proxy server: This server is used to intercept all messages entering and leaving the network.

3.3 Use backup

To reduce the damage which viruses does by creating regular backups of data and the operating systems on singular media which is kept unconnected to the system in most of the time, or either read-only or not accessible for other reasons such as using different file systems, CD, DVD or external hard disk. This way, if data or information is loss due to viruses, then can start on again by using backup which should preferably be recent. But for backups on removable media must be carefully examine before restoration due to the Gammima virus, for example, propagates via removable flash drives.

Chapter 4


A local area network (LAN) is set up to supply a networking capability to a group of computers in close proximity to each other such as in an office building, a school, or a home. LAN has become a very useful tool for a bunch of computers that need sharing resources like files, printers, games or other applications. A few LANs often connects to other LANs, and to the Internet or other WAN.

4.1 LAN can be infected by virus

LAN is a short form which stands for Local Area Network. Basically LAN is a small working group network composed of server and multiple computers. Each computer in a LAN is connected through server. The information transmission rate is, therefore, relatively high in LAN. The high data rate in turn inevitably provides an effective channel to the spread of viruses. Usually a virus in the LAN can spread through several channels as below:

- The openness of resources sharing in LAN is a loophole that leads to the direct infection of viruses.

- Normally several servers in LAN are low-end servers or general PCs. Therefore, these servers are not very powerful in performance and security features. So when a LAN attempts to transmit data through the virus-infected server, all the data transmission through the server will be infected and this would result in the infection of the entire network.

- If a virus has infected a computer in a LAN, any attempt to transmit data by the computer through a server would make the server vulnerable to the virus infection. Furthermore, any computers transmitting information through this sever will be at risk of getting infected.

- Any LAN users that do not have a solid knowledge of computer viruses protection would most likely cause the chance of recurrent infection.

To sum up, these unique features of the LAN are the main causes that speed up the transmission of viruses and mutual infection. The worst part is viruses are usually hard to clean thoroughly.

4.2 The possible treatment

Before being infected

There are some possible ways to prevent LAN from being infected by viruses as the following below:

Obtain a REAL TIME anti-virus solution from a major vendor and remain virus definitions up to date with the vendor of virus definitions from.

Plan at least weekly do virus scans on the network or personal computer. The users really should be working on this procedure more than once a week, but this is a bare minimum.

Carry on open folder and drive shares to a minimum. One of the first things that most viruses try to do is replicate itself. Stop damage to LAN by minimizing the number or network shares that user have connections to or available network shares.

Keep unknown downloads to a minimum. Most of user share or receive files overcome sort of P-2-P file-sharing application. Some of these files, although they appear to be ok, but viruses are really just waiting to be opened.

After being infected

However, when computer are already attracted by viruses, there are some methods that help to work out with the problem such as: when the PC is presenting that it is being infected, the user should disconnect the computer from network immediately. This obviously will minimize potentially-immediate infections on other PCs on the same LAN. To do this, the users have to do it fast, disable the LAN and unplug the LAN immediately after work.

Another way is to get as much information as possible about the specific virus that user commonly face and find out how to deal with it from the particular vendor’s site. It is very fortunate to users that a lot of these sites provide removal tools as well.

Chapter 5


Therefore, to prevent losing of data from virus, users should prevent download program or click on to unknown website or unknown source. In addition, there are several ways to protect computer from virus and other worm by use full version of antivirus. If computer always connect with other device, users should have data backup to make sure that you do not loss important data if your computer get affected by virus so when computer users can follow this method, the computer will not simple get attract by virus.