A Virus on your Computer

Posted By BrokenClaw on February 3, 2008

What happens if a virus gets into your computer? There are a whole range of effects that malicious software can have once it gains access to your computer. The differences between a virus, a worm and a trojan horse are explained elsewhere, but for the purpose of this article, we will use the term virus to mean all three. Also, we will use the term hacker to mean the person who sends out the virus or the person who benefits from the virus.

In the early days of computer software, a hacker was someone who would look at programming code and improve it by making it more efficient. Hacker was a term of respect. Over time, the connotation of hacker has declined and is now more closely associated with someone who gains unauthorized access to software, computers, and networks.

An Infected Computer

Some viruses have a simple purpose of destroying your computer files by deleting them or overwriting them with other files. For example, they might delete all of your photo or music files. If they affect the operating system files, they can make your computer unusable — unable to boot or unable to run applications. This type of virus really has no payoff for the hacker, other than some misguided sense of satisfaction from its destructive results.

The real power of viruses is the ability to obtain information about you or to control your computer remotely without your knowledge. Viruses of this type set up a system to “phone home” over your Internet connection. That is to say, they collect data from your computer and then send it back to the hacker automatically, or allow the hacker to connect to your computer. With access to your computer, they can override the protections of any firewall you may have installed, or even disable an anti-virus program. The hacker might create a hidden directory on your hard drive and use it to download large files, especially illegal or pirated media.

One example of software installed by a virus is called spyware, discussed elsewhere, which collects data about your web habits or copies all the email addresses from your email program.

Another example is called a keylogger, which is a program that runs in the background and records (logs) every letter (key) you type. By searching through the log, the hacker can discover all sorts of personal information such as your name, address, phone number, and websites you regularly visit. The hacker could use the data to create a customized phishing scheme, for instance, by knowing which online bank service or online merchants you already use. Even more damaging, the hacker could extract your usernames and passwords to those websites, or even extract your credit card numbers directly.

On a less personal level, the virus can turn your computer into a robot or zombie, which is a topic for another article.

Virus Removal Tools

Anti-virus programs, when kept up-to-date, are most adept at preventing viruses from getting to your computer. They are also fairly good at identifying markers left by viruses. However, once a virus has its hooks in your system, they are difficult to remove. The problem is that viruses today are very sophisticated programs which install software at the very basic elements of your operating system. They are not single files which merely need to be deleted. Even commercial programs can have difficulty removing all the remnants.

Another option for virus removal is a feature of the operating system called System Restore. When set up properly, System Restore periodically takes a snapshot of your system files and saves them for a certain period of time. The idea is that if something bad happens, you can reset your computer back to an earlier time before the bad thing happened. The success and failure of using System Restore to eliminate a virus is dependent of the type of virus and how quickly it is detected.

Unfortunately, the only sure way to clean your computer of a virus is to delete everything from your hard drive and start over. The process involves a procedure called re-formatting and then re-installing your operating system and all of your programs and all of your data files. Obviously it is not a trivial undertaking, and it requires a level of expertise that most home users do not have. This scenario stresses the importance of always having a backup of your personal files.

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