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  • Common modes of virus execution :
  • Virus trigger events and
  • direct attack are the common modes which cause a virus to create impact on the target system

How virus spreads ?

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  • Most viruses operate in two phases:

Infection Phase :

  • Developers of the virus decide when to infect host system’s programs Some infect each time they run and executed completely
    • Ex: Direct Viruses
  • Some virus codes infect only when users trigger them which include a day, time, or a particular event
    • Ex: TSR viruses - It get loaded into memory and infect at later
    • Stages

Attack Phase :

  • Viruses will have trigger events to activate and corrupt systems
  • Viruses will have bugs which replicate and perform activities like file deletion, and increasing session time
  • Viruses will corrupt the targets only after spreading completely as intended by their creators.
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  • The code or application will have .EXE File to Infect the Programs

Working of Virus: Attack Phase

  • Slowdown of PC due to Fragmented Files
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Why People create computer viruses?

  • Virus writers/creators will have variety of reasons in creating and spreading malware/or similar kind of viruses. Reason for creation viruses
    • Research projects
    • Pranks
    • Vandalism
    • To attack the products of specific companies
    • To distribute political messages
    • Financial gain
    • Identity theft
    • Spyware
    • Cryptoviral extortion
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Symptoms of Virus-Like Attack

  • If the system reacts in an unexpected manner, you can suspect a virus attack
    • Example: Processes take more resources and its time consuming
  • However, not all the problems can be done by the virus attacks. It can be a hardware problem too. Examples include:
    • Certain hardware problems
    • If computer beeps with no display
    • If one out of two anti-virus programs report virus on the system
    • If the label of the hard drive change
    • Your computer freezes frequently or encounters errors
    • Your computer slows down when programs are started
    • You are unable to load the operating system
    • Files and folders are suddenly missing or their content changes
    • Your hard drive is accessed too often (the light on your main unit flashes rapidly)
    • Microsoft Internet Explorer "freezes" - browser freezes
    • Your friends mention that they have received messages from you but you never sent such messages

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