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Understanding Computer Viruses

Like human body, computer systems are also vulnerable to attacks by techno-pathogens, which may partly or permanently damage their functional ability. The major and, perhaps, the most popular techno-pathogen happen to be computer viruses. A computer virus is a dangerous computer program with the characteristic feature of being able to generate copies of itself, and thereby spreading. Additionally, most computer viruses have a destructive payload that is activated under certain conditions. In cyber lexicography, the word virus has been derived from and used in the same sense as a biological virus. A computer virus spreads itself from one computer to another, when its host comes in contact with an uninfected computer, which may happen either through the internet, or through the removable media such as a floppy disk, CD or a USB drive. Additionally, a computer virus can also proliferate through the infecting files on a network file system or the file systems that are accessible to other computers. The present scenario, with a majority of computers being connected to the internet, the conditions are most favourable for the spread of computer viruses.

Understanding the way a computer virus works becomes much easier once we understand the functioning of a biological virus. A biological virus in itself is not a living thing. It comes alive once it penetrates a living cell. Once there, it uses the host cells energy and cellular machinery to replicate itself. The replicated progeny then ruptures the host cell and carries on the infection further by looking for new targets. A computer virus works on the same line. It must piggyback on top of some other program or document in order to get executed. Once it is running, it is then able to infect other programs or documents.

On the basis of their unique features, viruses can be subdivided into various types. A ‘macro virus’ is often written in the scripting languages for programs such as Excel and Word, which spreads by infecting documents and spreadsheets and is platform-independent. Some prominent macro viruses are Bablas, Relax, Melissa A, etc. Then there are ‘network viruses’ which quickly spread across a Local Area Network (LAN) or over the internet. Some notorious network viruses are Nimda and SQLSlammer. A ‘logic bomb’ uses a code that lies inert until certain specific conditions are met, which will trigger certain functions such as deleting files. The infamous ‘Friday the 13th’ was a typical logic bomb. A ‘cross-site’ scripting virus (XSSV)’ is a virus that spreads between vulnerable web applications and web browsers creating a symbiotic relationship. On the other hand ‘sentinel’ is a state of the art virus which empowers its creator or perpetrator with remote access control over the computers that are infected. E-mail viruses spread through e-mail messages. They usually duplicate themselves by automatically mailing themselves to the people in the victim’s address book. Trojan horses are simply the programs that claim to do one thing but instead do damages when they are run. Worms are software that uses computer networks or security holes to replicate themselves.

The effects of computer viruses are varied and damaging. They can damage or delete the data stored in the computer. They can use the infected computers to spread to the uninfected ones. Computer viruses can also alter or delete the files stored in the computer. They can cause the infected computers to crash or may simply blink a message on the screen. Mainly, the most disastrous effect of a computer virus is the deletion or damage to the precious data stored in the computer. Besides the transmission techniques, viruses also have evasion techniques. This means that a virus also has a defence technique which can make its detection very difficult in the infected computer. Some viruses can even disable the Antivirus software installed in the computer.

A good and authentic antivirus software is the most important line of defence against viruses. However, it is not only important to install antivirus software in the computers, but equally important is the task of updating it on a regular basis. Day in and day out, many new varieties of viruses are invading the internet and antivirus software providers mostly update their products from time to time. Besides, relevant precaution needs to be exercised, while handling one’s e-mail.

However, once a computer gets infected by a virus, the chances are that the data stored in the deleted files may still be intact on the hard drive, unless and until that file gets overwritten. It is possible to retrieve this data by soliciting the help of specialists apt in the techniques of data recovery. Lost data is certainly not hundred percent recoverable, but data recovery technicians can often recover surprisingly high percentage of data on the damaged media.

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