Popular Boot and Trojan Viruses That Caused Havoc

Any anti-virus software review draws a distinction among the kinds of threats that may affect your system. As a consumer conducting an anti-virus software comparison, make sure that any package you are considering using will offer a maximum level of protection. All viruses are not the same, they differ in the way they are deployed and propagated or in the type of damage they cause. Two types of malicious code, which you should be aware, are boot viruses and Trojans.

Boot Viruses

One of the prime targets for malicious code or virus authors is the boot sector of a computer's hard disk that contains the operating system programs. Replication and propagation are main viral goals. A virus that attacks the boot sector will run automatically each time the computer starts and before any other process is activated. Although floppy disks are used less frequently now due to their limited size, early in the computer revolution boot viruses were often spread through users exchanging disks. Viruses hid in the disk volume boot code even in the absence of system files on the disk. In fact the first PC virus in 1986 was a boot sector virus called (c) Brain.

Trojans

A Trojan poses as a benign application. They do not replicate themselves but they can be just as destructive as any other virus. Trojans trick the user into opening them by appearing to originate from a legitimate source. Some are designed to be annoying by displaying graphics, playing a sound repeatedly, or changing the desktop. Others damage and delete files or create a so-called "backdoor" to allow unauthorized, covert access to the system thus allowing for the potential compromise of personal or confidential information.

What are some of the Popular Boot Viruses and Trojans?

There are literally thousands of viruses of all types that have already been identified and new ones are being written daily. Consequently anti-virus software ratings should include a consideration of the update process. Read any anti-virus software review carefully and make sure you are using a package that will keep your virus definitions regularly updated to effectively protect your system.

Boot Viruses

Again, due to the decreased use in 3.5" floppy disks, the risk factor on all these boot viruses is now considered to be low. They do, however, illustrate the range of potential annoyance and damage from this class of malicious code.

Form

On the 18th of every month the Form virus causes a clicking sound when a key is pressed. Although it is not intended to cause real damage, Form can make a system hang and under some circumstances by overwriting the second sector and original DOS boot sector on the hard drive, will make it impossible for the drive to boot.

Disk Killer

Disk Killer sits on the hard drive of a system for 48 hours of usage and then encrypts all of the data on the entire drive with a routine that randomly changes byte values. If the encryption is allowed to finish, the data cannot be recovered.

Stoned. Michelangelo

This virus infects the DOS boot sector of floppy disks and the master boot record of a system's first hard drive. On disks, corrupted file names begin to appear and data can be overwritten. On hard drives the virus activates on March 6 each year. If an infected machine is booted on that day, the virus silently overwrites data on the first 17 sectors of the first 256 cylinders of the drive. The material cannot be recovered.

TROJANS

Unlike boot sector viruses, Trojans are highly prevalent and easily transmitted in email messages. The absolute best advice in regard to email and attachments is simple -- don't open them. If you don't know or cannot verify the origin and purpose of the attachment, don't open it. Examples of some Trojans are listed below.

Trojan. Archiveus

This Trojan places password protection on files and asks users to buy items from specific websites in order to get the password. This virus was discovered as recently as May 6, 2006.

Trojan. RealSearch

This is a good example of a nuisance Trojan. When activated, Trojan.RealSearch displays fake system alerts regarding malicious and dangerous activity on the infected machine.

Trojan. Emcodec.B

This Trojan masquerades as an installer for a media codec required for the Windows Media Player. It is actually serving as a vehicle to execute a copy of a member of the Trojan.Zlob family of viruses on the machine which allows remote access to the system.

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