Computer Viruses

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Computer Viruses

• Susan Rascati
• CS30 Section 11
• George Washington University

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What is a Virus?

• A virus is a self-reproducing program that can
  infect other programs by modifying them to
  include, a possibly evolved, copy of itself.

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What is meant by infection?

• A virus infects by inserting itself into the
  chain of command so that when one attempts to
  execute the original program the virus as well
  (or in more extreme cases, instead) is executed

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3 Main Components

• INFECTION The method in which the virus spreads
  
• PAYLOAD What the virus does besides replication.
• TRIGGER The routine that decides when the
  payload is delivered.

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Mandatory Components

• Only the INFECTION mechanism is mandatory
  component of a virus

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Viral Damage
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Deliberate Damage

• Deliberate damage is what is inflicted by the
  virus payload
• Can range from completely benign results such as
  running the screen message I WANT A COOKIE to
  corrupting files and destroying a hard drive

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Accidental Damage

• Damage is caused when a virus attempts to attach
  itself to the system
• The virus can accidentally corrupt areas and
  inadvertently inhibit a user from opening files
  or booting up the computer
• Such actions are considered accidental because
  they are not the part of the payload mechanism

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Incidental Damage

• All viruses, even benign ones, cause
• some loss of computer performance
• Memory
• Disk space
• Clock cycles

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How to prevent a virus

• Avoid opening email attachment from senders you
  do not know
• Be very particular about the type of freeware and
  software that you chose to use and download
• Use anti-virus software to scan ALL files and
  documents before they are opened on the hard
  drive

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Anti-Virus Software

• The greatest method of virus prevention is
• anti-virus software.
• It will scan your hard drive every time the
• computer is turned on. Ideally, these programs
• search for behaviors characteristic to viruses,
• isolate the infected files, and remove the virus
• from the software.

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Update Anti-Virus Software

• In order to ensure complete protection, one must
  do more than simply buy and install such programs
• While most software can identify the most common
  viruses, on average 3-5 new strains are
  discovered every day

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Update Anti-Virus Software

• Many anti-virus companies such as Symantec and
  McAfee maintain websites that contain the most
  up-to-date virus information
• The most recent virus information can be
  downloaded to your existing software allowing you
  to detect the new strains
• These websites also offer instruction on how to
  remove certain viruses should your computer
  become infected

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OH NO! I have a virus!

• If all prevention methods fail and your
• computer manages to get infected dont panic!

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Is it even a Virus?

• It may look like a virus, but it might be a JOKE
  or a TROJAN HORSE
• The main difference Viruses modify other files,
  jokes and Trojan horses exist in only one file
  and thus can be removed through the deletion of
  that file

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How to Tell

• Most likely it is a Virus if
• It reads as a common, older virus
• Scanner finds it in file or boot sector today, it
  wasnt found yesterday, and you have not updated
  your scanner files
• Scanner finds two instances of the virus in the
  same computer

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How to Tell

• Most likely it is NOT a virus if
• Your scanner only finds one infected file, and it
  is a file you use all the time
• Scanner only identifies something as a possible
  virus

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Virus vs. Hoax

• Dont believe all that you read.
• Many emails you receive warning of deadly viruses
  are HOAXES they describe phony viruses!

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It is Probably a Hoax if it

• Reports that it will cause horrific damage to the
  PC
• Uses very technical language to which the user is
  most likely not familiar
• Is written in very motive language, such as all
  capital letters to influence its power and
  urgency
• Tells you that you MUST email it to as many
  people as possible in order to avoid an awful,
  viral fate!

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If it definitely is a virus

• Dont panic, instead Contain, Control, Kill
• First you want to prevent further spread of the
  virus.
• Limit the use of the infected workstation
• Learn everything you can about the virus so that
  you are fully prepared for all that it might do
  to the PC

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Kill the Virus

• Search for solutions, either on-line at
  subscriber anti-virus sites such as
  www.service.symantec.com
• or public sites such as www.virusinformationcen
  ter.com
• Follow the directions for virus extermination
• If you cannot alone exterminate the virus, call
  in the experts