1. Computer Viruses
Author: Alyse Allen

2. Computer Virus Very common Millions of different ones exist
A computer program that can replicate itself and spread from one computer to another causing harm

3. Three Different Types Macro Viruses Stealth Viruses
Polymorphic Viruses

4. Macro Viruses

5. Macro
Symbol, name, key, etc. that represents a list of commands, actions, or keystrokes
Can be very useful

6. Example If you type a lot of letters
Set up a macro that defines all the keystrokes necessary to begin your letter
Name, address, etc.
Press the assigned key/keys and your letterhead appears
Like batch files

7. Macro Virus Computer virus
Usually infects a Microsoft Word document or spreadsheet
Causes a sequence of actions to be performed automatically when the application is started or something else triggers it.
Most of the time it is relatively harmless

8. Macro Virus
Written in a language that is built into the software application
Replaces normal macro commands with the virus

9. How?
Virus replaces the regular commands with the same name and runs when the command is selected.
If the infected macro is auto-executable, the macro is opened and the virus executed without the user’s knowledge

10. How is Macro Viruses spread?
Often through s
Discs
Networks
Modems
Internet
**HARD TO DETECT**

11. Macro Virus More easily spread
Depends on the application, not the operating system
Can infect computers running all different operating systems
Some of these viruses can be detected through antivirus software but not all.

12. Melissa Virus Found March 26, 1999 Not originally designed for harm
Overloaded servers and mail systems were shut down
Written by David L. Smith
He named the virus after a stripper he met
Virus was embedded into a word document entitled list.doc
Sent out as an

13. What did Melissa do?
Once opened, the macro virus would run and attempt to mass mail itself
Collected the first 50 address book entries and forwarded the to them with the list.doc attached
Subject line of the read: “Important message from [name]”
Body read: “Here is that document you asked for…don’t show anyone else ;-)”

14. Stealth Viruses

15. Stealth Virus Virus that hides from antivirus software by:
a. masking the size of the file that it hides in
b. temporarily removing itself from the infected file and placing a copy of itself in another location on the drive, and replacing the infected file with an uninfected one that it has stored on the hard drive.

16. How a stealth virus works
Fools the antivirus software by catching its requests to the operating system to open a file.
The virus can then provide (open) a clean version of the file to the antivirus software
The antivirus software is tricked and the virus won!

17. Frodo Virus Infected file is executed Virus becomes a memory resident
Infects any file accessed by the user with the .com or .exe extension
On Sept. 22, it attempts to place a Trojan on boot sectors
Trojan displays the message “FRODO LIVES”
Frodo is a Lord of the Rings character whose birthday is September 22nd.

18. Polymorphic Viruses

19. Polymorphic Virus One of the more complex computer viruses
Virus that changes its virus signature (binary pattern) every time it replicates and infects a new file in order to keep from being detected by an antivirus software

20. Effective Polymorphic Virus
A coder chooses from a number of different encryption schemes that require different methods of decryption
Only one scheme will remain visible in all instances of the infection.
If virus scanner is based on string-driven detection, many different strings would have to be detected (one for each probable decryption scheme).

21. Most complex form AKA: Big Brother of all polymorphic viruses
Relies on its Mutation Engine – type of object module
Mutation Engine allows ANY virus to reach a polymorphic state by implementing specific codes to the program source code and linking modules able to generate random numbers

22. Polymorphic Viruses Very harmful Can completely corrupt your system
Can go undetected for months

23. Tequila 1991 First widespread polymorphic virus found
Polluted local executable files
When users ran infected program(s):
a. appended itself to the hard disk’s file storage area
b. altered Partition data c. modified the Master Boot Record to “point” to itself

24. How the infected computers suffered
Had File Allocation Table errors
Terminal data loss

25. How do you protect your PC from viruses?

26. The answer is VERY simple…

27. Convert to a MAC

29. Take precautions to secure it
Make sure your operating system is up-to-date by: a. installing the latest patches and b. service updates
Use antivirus protection
Use a firewall
Lock down your wireless internet

30. References http://en.wikipedia.org/wiki/Computer_virus
on/macro-virus
virus.html
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on/Melissa-virus

31. References
5-common-types-virus html
virus.html
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