COMPUTER VIRUSES AND SECURITY
COMPUTER VIRUSES
Virus is a self-duplicating computer program that interferes with a computers hardware or operating system. They range from being merely irritating (or disturbing) to the very destructive. Computer viruses activate when the instructions (payload of the virus) or executable code that run programs are opened. Once a virus is active, it may replicate by various means and infect the computers files or the operating system. For example, it may copy parts of itself to floppy disks, to the computers hard drive, into legitimate computer programs, or it may attach itself to e-mail messages and spread across computer networks by infecting other shared drives. Viruses attached to e-mail messages can infect an entire local network in minutes (this is specifically called WORM).
a. Internet eavesdropping snuffers which intercepts internet messages sent to other computers b. Password guessers that tries millions of combinations of characters in an effect to guess a computers password. c. Vulnerability testers that look for software weaknesses d. Computer services saturator e. Automatic computer virus generator.
Types of Viruses
a. A boot sector virus stores itself at the start of a disk and becomes activated by reading, starting or restarting the computer when that disk is in the boot drive. b. A file infector virus attaches itself to program files i.e. files that give instructions to a computer. These files usually have extensions like exe, com, or bat. When the program is run, the virus executes. c. A macro virus affects data files, especially Word documents and Excel workbooks. This virus type accounts for the vast majority of infected files. When the infected document is opened and the macro are run, the virus is triggered and can perform system operations such as creating or deleting files or writing into already existing files and thus have the potential to cause a great deal of damage. d. Worm or an email virus (for the purpose of this guide) is not really a virus at all (in that it is not self replicating) but a chain letter phenomenon sent through email. The message will, for some reason or other, tell you to pass this message on to as many people as possible. Hoax virus alerts are typical examples of chain emails. These are distinct from viruses in that they do not have host file like most other viruses but are carried on the internet and can spread from one computer to another by themselves without the need for a user to assist the process by giving someone an infected file or disk. They are usually spread through the Computer Training Expert Solution Consults Computer Basics
internet as an attachment. e. Trojan horses are programs that have some hidden, generally malicious functionality that the computer does not expect. They claim to be a thing (e.g. an audio for example), when they are actually another (e.g. code that will overwrite a portion of your hard disk). They do not run their own like a virus does but rely on tricking the user to run them. They dont also replicate themselves which is a major distinction between a virus and a Trojan.
How Viruses are Spread
Viruses are spread by running infected programs or opening infected files. This can occur by using any of the following methods:
Passing floppy disks from PC to PC
Downloading (copying) infected files from the Internet
Opening an email attachment
Booting a PC with an infected bootable disk.
Computer viruses work in two phases: infection phase and the attack phase.
Infection phase: in order to infect a computer, a virus has to possess the chance to get executed before it can infect the computer system and spread to others. Events that can trigger the execution of virus are included above.
Attack phase: viruses do destructive things such as deleting files, erasing data on a hard disk, sending random emails or slowing down the processor by sending millions of looped instructions. Since most users will try their best to delete the virus once it launches the attack, most virus delay revealing their presence by launching their attack only after they have had ample opportunity to spread. This means the attack may be delayed for a long time after the infection.
Prevention of Computer Virus
Computer users can prepare for a viral infection by creating backups of legitimate original software and data files regularly so that the computer system can be restored if necessary. However, the best prevention may be the installation of current and well-designed antiviral software. Such software can prevent a viral infection and thereby help stop its spread.
Or obtain a virus checker for your own machine then register the program with the manufacturers. They will regularly send you updated versions of the software while your agreement is current. New viruses keep appearing, so out of date virus software will not protect you and the checker is essential. Install the available security patches, particularly for Microsoft products. Keep your floppy disk write-protected whenever possible. If you are really cautious, change the set-up option in your computers BIOS so that it will always boot from the hard disk, not from floppies. Write protect MS Words Normal template to get limited protection against macro viruses. This template will be a file called Normal.dot. Select the Read Only bod. Note that this will not disinfect existing infected files.
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