Viruses are malicious computer programs that can spread from one computer to another by infecting files. They typically spread through removable media like floppy disks, downloading infected files from the internet or email attachments, or installing software that contains viruses. Common types of viruses include Trojan horses, which disguise themselves as legitimate programs but perform hidden malicious actions without the user's knowledge or consent, and worms that can automatically spread to other computers. Salami attacks involve small, repeated thefts that individually go unnoticed but collectively result in significant losses.

2.  In computer technology,viruses are malicous
software program,a form of malware.By
defination,viruses exist on local disk and spread from
one computer to another through sharing of “infected”
files

3.  Using a flopppy diskette from a machine that has a virus.
 Downloading a file from the internet(or buletin board) that
contains a virus.
 Getting an email attachment that contains a virus
 Installing software purchased from a store or mail
warehouse.While this is the rarest of the ways,software
vendors have been found to ship their software with
viruses (unknown to them of course) on the insatallations
diskettes or cd-roms

4.  Data diddling
 Salami attack
 Internet time theft
 Logic bomb
 Virus / Worm attack
 Trojan horse
 Cyber pornography

5.  Trojan horse is a program that does something
undocumented which the programmer intended,but
that the user would not approve of if he knew about
it.
 According to some people,a virus is a particular
case of Torjan Horse,namely one that is able to
spread to other programs.
 A simple example of a Trojan Horse would be a
program named “Waterfalls.Scr”claiming to be a
free waterfall screensaver which,when run instead
would allow access to the user’s
computer.computer.

6. # Trojan Horse playloads are almost always designed to
do various harmful things,but could be harmless.They are
broken down in classification based on how they breach
system and the damage they cause:
# The eight main types of Trojan Horse payloads are:
1.Remote access
2.Data destructive email sending
3.Downloader
4.Proxy Trojan(disgusting others as the infected
computer)
5.FTP Trojan(adding or copying data from the infected
computer)
6.Security software disable.

7. 1. Denial-of-service attack (DoS)
2. URL Trojan (directing the infected
computer to only connect to the
internet via an expensive dial-up
connection).

8. SALAMI ATTACK
♥This attack is used for the comission of financial
crimes.
♥The key here is to make the aliteration so
insignificant that in a single case it would go
completely unnoticed.
E.g:A bank employees inserts a program into
the bank’s serves that deducts a small amount of
money from the account of every customer.
Why salami attack persist?
♥Computer computations are notoriously subject
to small errors involving rounding and
truncation,especially when large number are to
be combined with small ones.

9. CONCLUSION
 Computer virus can effect
the computer system.It can
copy itself and infect without
permissions or knowledge of
the user.