21.2 Malicious Software: Viruses, Worms, Trojan ...


Malicious programs are malware include threats such as computer viruses, worms, and Trojan horses.
A computer virus is a software program works as rogue and attaches itself to other data files or even programs so as to be executed without user knowledge.
Most viruses of computer deliver a payload which may be good (such as instructions for displaying messages or images) or may be destructive like destroying programs and data, plugging memory, reformatting computer, or causing improper programs run.
The east way for viruses to spread from computer to computer is by taking an action from users like sending e-mails or copying infected files.
Worms are one of the most attacks, which can copy themselves several times from computer to other through a network.
Computer worms spread much more than computer viruses because they do not need to be attached to software programs or files, they can operate on their own without relying on human behavior.
Worms can destroy programs, data, and cause harm to computer networks.
Internet is a suitable environment for worms and viruses to spread through files of downloaded software, files attached to e-mail, and instant messaging.
Also viruses can be carried from infected disks and machines. Mobile phones today are targeted by more than 200 viruses and worms, such as CABIAR, Comwarrior, and Frontal A.

21.2 Malicious Software: Viruses, Worms, Trojan ...


A Trojan horse is a software program which emerges to be benign.
It is not a virus but the virus and other malicious code use it as a way to be introduced into a computer system.
There are types of spyware act as malicious software programs. Intruders install these programs for monitoring user web surfing activity, accessing data, and for picking up personal information such as credit card numbers and users' passwords.
Other types of spyware work to slow computer performance.