SECURITY THREATS

Computer threats can come from many ways either from human or natural disasters. For example, when someone is stealing your account information from a trusted bank, this threat is considered as a human threat. However, when your computer is soaked in heavy rain, then that is a natural disaster threat.
TYPE OF SECURITY THREATS

MALICIOUS CODE -Malicious code is also known as a rogue program. It is a threat to computing assets by causing undesired effects in the programmer’s part. The effect is caused by an agent, with the intention to cause damage.
a) VIRUS
a program that can pass on the malicious code to other programs by modifying them
attaches itself to the program, usually files with .doc, .xls and .exe extensions
destroys or co-exists with the program
can overtake the entire computing system and spread to other systems
b) TROJAN HORSE
a program which can perform useful and unexpected action must be installed by users or intruders before it can affect the system’s assets an example of a Trojan horse is the login script that requests for users’ login ID and password the information is then used for malicious purposes
c) LOGIC BOMB
logic bomb is a malicious code that goes off when a specific condition occurs.
an example of a logic bomb is the time bomb it goes off and causes threats at a specified time or date
e) TRAPDOOR OR BACKDOOR
a feature in a program that allows someone to access the program with special privileges
f) WORM
a program that copies and spreads itself through a network
HACKER-Hacking is a source of threat to security in computer. It is defined as unauthorised access to the computer system by a hacker.
Hackers are persons who learn about the computer system in detail. They write program referred to as hacks. Hackers may use a modem or cable to hack the targeted computers.
NATURAL AND ENVIRONMENTAL THREAT-Computers are also threatened by natural or environmental disaster. Be it at home, stores, offices and also automobiles. Examples of natural and environmental disasters:

THEFT-Two types of computer theft:
Computer is used to steal money, goods, information and resources.
Stealing of computer, especially notebook and PDAs.
Three approaches to prevent theft:
prevent access by using locks, smart-card or password
prevent portability by restricting the hardware from being moved
detect and guard all exits and record any hardware transported

http://www.albany.edu/its/security_threats.htm
http://search.yahoo.com/search?p=SECURITY+THREATS&fr=
https://www.securitymetrics.com/securitythreats_home.adp