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Explain how a computer virus works.
A computer virus exists in an infected program. When a user runs an infected program, the computer copies the program into RAM. The viral code runs before the user-initiated program. The virus copies itself to another part of RAM so that it can continue to run after the user starts running other software. Then the virus passes control back to the infected program. When the user runs a different program the virus begins running again, then inserts itself into that software.
What is a computer worm?
Worms are parasitic computer programs that replicate but do not infect other computer program files. They can create copies on the infected computer or send copies to other computers via a network. The often spread via e-mail or chat apps.
What is a Trojan Horse?
It is a malicious program that pretends to be a benign application. One type of Trojan Horse (logic bomb) is set to execute whenever a specific event occurs (time/date, change in a file, etc).
Describe three techniques used to combat computer viruses.
- 1) Generic antiviral program - prevents activities that are likely to arise from a virus in action. Probably won't eliminate a virus but can prevent it from infecting additional programs or interfering with computer's normal operation.
- 2) Signature scanner - searches disks for fragments of program code that appear in known viruses.
- 3) Antiviral snapshots - capture mathematical fingerprints of crucial programs and data. If these are later changed, a viral infection is suspected. Original fingerprints can be used to recover an infected program to its original condition.