Computer Virus

1
Computer Virus

• Software programs written by someone that needs
  to get a life
• Can range from being a nuisance to causing major
  destruction and recovery time
• Software packages can be infected

2
Viruses Hide in

• Another computer program that executes so that
  the virus program can be placed into main memory.
• Typically, viruses come from programs on floppy
  disks or networks.
• Very complex viruses can write themselves in
  between hard disk sectors making them very
  difficult to detect.

3
Virus Types

• Trojan Horse - contained inside of another host
  program. Often date activated. White collar
  sabotage.
• Worms - may not be an executable program itself
  but duplicates in main memory and hard disk
  space. Slows down the operating system.
• Stealth virus - pretends to be another program
  that should be on the computer

4
Virus Components

• Replication code - how it does what it does
• Marker - set of codes that virus looks at to
  determine if the file has been infected
• Kernel - code that controls task manipulation and
  replication
• Overwriting vs non-overwriting replaces an
  existing program file vs appending to it

5
Elimination and Protection

• Scanner software - shield software scans all
  data coming into a computer system looking for
  known or suspected viruses. Known viruses are
  detected by some recognizable character string
  in the virus computer code. Suspected viruses are
  detected whenever the virus program tries to do
  something weird, like attach to an existing
  program or reuse disk space reserved for the
  operating system.
• Cleaner software - can try to restore infected
  files back to a useable state. Requires booting
  from a clean, write protected floppy disk May
  take a lot of time.
• Detection software - detects the presence of a
  virus on an infected disk
• Typical packages McAfee, Dr. Solomon, etc