Wednesday, September 5, 2012

Computer Virus


A computer virus is a program or piece of code designed to hide in the background and to perform one or more of the following activities
·         Replicate itself
·         Attach to other programs or instructions
·         Perform unintended actions
In order to be called a “Virus” a program needs not to perform outright damage. Some virus programs do not cause any damage to the computer. One of the most costly types of damage that a virus can cause is the modification of the accuracy of data.
Another embarrassing effect of some viruses is the disclosure of confidential documents, passwords, PIN numbers etc… to Internet websites and e-mail to external parties.  Until all instances of an affected virus are deleted, the virus maintains the capability of self-replication and the process may start all over again.
A virus needs a place to live, "host" - the particular hardware and software environment on which it can run. When an infected program is executed, the embedded virus is executed too, thus propagating the "infection" without the knowledge of the user. Computer viruses are designed to attach to many files or disks without being detected and to cause damage to data held on the affected computer.  
Some viruses also slow down a users system, disable certain functions, or cause erratic system behavior.  Computer viruses often infect many programs on the same system or even parts of the operating system.  Users can unknowingly transmit a virus from one system to another by copying infected program files from one machine to another or by using an infected program downloaded from the Internet.
The first common computer virus, called “Brain” virus, was written in 1986 by two brothers in Pakistan. The majority of viruses are written by hackers. Some of the known viruses and their effects are given below.


Some of the main reasons for writing viruses are,
  • Hacking
  • To prevent copying software
  • Revenge : Employees may plant “Time Bombs” in programs
  • Fraud : Viruses may allow access to an otherwise secure system
  • Political and terrorist motives
  • Commercial sabotage : Damage the reputation of a competitor
  • Warfare : Incorporate a virus to an enemy’s computer.
Viruses can be transmitted from one system to another through various media types such as;
  • Floppy disks
  • Tape backups
  • Internet
  • Software
Virus Symptoms
Some of the symptoms that a computer will show up when infected with a virus are listed below.
  • Programs take long time to load than normal.
  • Computer's hard drive constantly runs out of free space.
  • The floppy disk drive or hard drive runs when you are not using it.
  • New files keep appearing on the system and you don not know where they came from.
  • Strange sounds or beeping noises come from the computer or keyboard.
  • Strange graphics are displayed on your computer monitor.
  • Files have strange names you do not recognize.
  • Unable to access the hard drive when booting from the floppy drive.
  • Program sizes keep changing.
  • Conventional memory is less than it used to be and you cannot explain it.
  • Programs act erratically.
Components of a Virus
A virus comprises of four general components
  • The replicator (or engine): replicates the virus.
  • The safeguard : prevents the detection and the removal of the virus
  • The trigger monitor: Monitors for a specific condition to deliver payload. These specific conditions may be the arrival of a particular date, time, keyboard stroke, etc.
  • The payload: the action it does apart from propagation. This action may be an amusing action or malicious action resulting in distraction from the current work or destruction of data.

2 comments:

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