### aggregation | package | computer programme:

Computer virus
* All computer viruses are manmade and come in many forms.
* Computer Viruses Consider the set of programs which produce one or more programs as output.
* Most computer viruses come in the form of executable files
  - fall into one of two categories - benign or malignant
* Some computer viruses are destructive, permanently damaging data files or programs on a computer
  - intentionally malicious
  - can take time to reveal themselves
  - cause damage due to poor programming and bugs in the viral code
  - come hidden in public domain games
  - do nothing but replicate themselves
* act much like human viruses.
* are a concern to everyone
  - constant problem in the modern world
  - leading security threat to Internet-connected networks
  - real threat to any computer with public access
  - serious problem in today's cyber world
  - threat to the security and the integrity of the computer system
  - very real threat to computing today
  - always present somewhere in a disk or computer system ready to strike
  - among the most pervasive threats to government systems
  - analogous to biological viruses
  - another class of time and resource wasters
* are computer programs or macros within documents
  - programs, just like any other programs
  - software programs just like spreadsheets and word processors
  - dangerous
  - everywhere
* are extremely common
  - minute programs that latch onto another program and then copy themselves
  - more common and more dangerous than ever before
  - much like real viruses
  - never airborne
  - one of the unforeseen byproducts of the information age
  - potentially dangerous and can be highly infectious in a network environment
* are programs created with malicious intent that cause havoc to computer systems
  - designed to replicate on their own
* are real and a force in our lives that have to be understood and dealt with
  - they are becoming more and more insidious
  - self-propagating programs that infect other programs
  - sets of code, or instructions, written in computer-language
  - similar to biological viruses
  - simply small computer programs that have as their sole aim to do harm
  - small programs that attach themselves to other programs or to parts of disks
* are the most common and well-known attack against computers
  - microcomputer security breach
  - famous members of quite a large collection of electronic beasts
  - unauthorized code pieces that can damage data and cause system downtime
* are very common
  - rare
* are, in their most innocuous form, a type of Internet vandalism.
* can act in many different ways
  - also cause any number of problems, including a system crash
  - attack any operating system and computing architecture
* can be a serious problem in any computing environment
  - destructive or non-destructive
* can cause a lot of grief, embarrassment and downtime
  - loss of data
  - significant damage
  - circulate via e-mail but only in attachments
  - destroy data on hard disks or floppy diskettes
  - do anything a legitimate software program can, and do it in secret
* can have a costly effect on companies
  - devastating effect on an organisation
  - make a computer work less efficiently or even wipe out the hard drive
  - modify programs, delete files and erase the contents of hard drives
  - range from simply annoying to seriously destructive
  - spread through electronic messaging systems
  - waste time and can destroy data
* get their name from their biological counterparts, true viruses.
* infect a variety of different subsystems on their host computers and software.
* leak their way in and out of computer systems within nano seconds.
* reproduce using the hardware and software already present on computers.
* run on a variety of machines under different operating systems.
* spread in three general ways
  - most rapidly when people are unaware they are at risk
* strike without warning and always result in loss of productivity.
* travel by attaching itself to other programs and reproducing
  - way of disks, Internet downloads, and most commonly e-mail attachments
* vary in the degree of harm that they can cause.
+ Self-replication: Biological reproduction :: Technology
  * Other kinds of replication occur. RNA viruses use the mechanism of a cell to replicate their own RNA strand and make its protein coat. Viruses can only reproduce by taking over the reproductive machinery of cells through a process of infection. Computer viruses reproduce using the hardware and software already present on computers.