Computer Viruses

1
Computer Viruses

• Dont let it infect you and your PC

2
How Bad Are They ?

• Afflict at Least a Million computers a year
• Users spend several million dollars annually on
  anti-virus products services
• 98 of North American businesses have been
  infected by over 6,000 types of viruses currently
  cataloged

3
So Why is it called a Virus ?

• Called a virus because they share some of the
  same traits as a biological viruses
• Passes from computer to computer like a
  biological virus passes from person to person

4
Categories of viruses

• Four main categories
• Common Viruses
• E-mail viruses
• Worms
• Trojan horses

5
HumSo how do viruses work?

• Start off by being a small piece of code attached
  to a popular game or word processor
• Once you run the infected program the virus is
  loaded into your computers memory
• It then looks for other programs on disk or file
  and secretly codes itself in with that new file

• Next time you run any of the two programs the
  virus spreads to another file and location
• It continues to spread by passing files onto
  friends thru disks or being loaded onto bulletins
• Viruses are about replication, replication,
  replication, and even more replication

6
E-mail viruses

• Viruses that move around in e-mail messages
• Replicates itself by automatically mailing itself
  to dozens of people in your address book

7
Worms

• Small piece of software that uses computer
  networks and security holes to replicate itself
• A copy of the worm scans the network for another
  machine that has a specific security hole
• Then copies itself to the new machine using the
  security hole and so on..

8
Trojan Horses

• Not a traditional virus
• But are simply a computer program
• A program that claims to be one thing (like a
  game) but instead does damage to your system once
  you run it (like erasing your hard drive)
• One good thing about Trojan horses is they cant
  replicate automatically

9
Types of viruses

• Three main types of ways viruses can effect your
  computer
• Macro
• Boot
• Parasitic

10
Macro

• Is an instruction that carries out program
  commands automatically
• Programs such as word processing, spreadsheets,
  and slide presentation applications use macro
• Once program is used it copies itself to computer
  and resides in the machine
• This is the most simplest and most commonly used
  virus

11
Boot Sector

• The 1st software loaded onto your computer
• Resides in your disk, either hard disk, floppy,
  or CD
• When computer turned on hardware automatically
  locates and runs boot sector program
• Boot sector viruses infects computers by
  modifying the contents of the boot sector

• It replaces the legitimate contents with its own
  infected version

12
Parasitic

• Attach themselves to programs also known as
  executables
• When program is launched the virus covertly goes
  first then the program
• Computer understands it as apart of the program
  allows it to go on and replicate itself, install
  into memory, or release its payload

13
What is the Payload ??

• This is where a viruses becomes a bad, very bad
  boy
• It is the destructive or attack phase of the
  virus
• Can be a number of things from silly little
  messages on your screen to crashing your whole
  system and erasing your entire memory from the
  hard drive

14
How to tell if you got a virus

• Unusual messages or displays on your monitor
• Unusual sounds or music played at random times
• System has less available memory then it should
• A disk or volume name has been changed
• Unknown programs or files have been created
• Some of your files become corrupted or suddenly
  dont work properly

15
Ways to prevent an infection

• Virus protection software, anti-virus software,
  or virus check
• Keep your anti-virus software current and check
  for updates on your product
• Dont open any un-trusted e-mails with
  attachments and delete it immediately

16
Ways to get rid of a virus

• Only two ways to get rid of them
• You can try to clean and disinfect it
• If that doesnt work your only option is to
  delete the files from your system