Common types of Malwares

Malware is a short form of Malicious software.Some common and dangerous malware known to us are:

VIRUSES
A computer virus is a type of malware that propagates by inserting a copy of itself into and becoming part of another program. It spreads from one computer to another, leaving infections as it travels. Viruses can
range in severity from causing mildly
annoying effects to damaging data or
software and causing denial-of-service (DoS) conditions. Almost all viruses are attached to an executable file , which means the virus may exist on a system but will not be active or able to spread until a user runs or opens the malicious host file or
program. When the host code is executed, the viral code is executed as well. Normally,the host program keeps functioning after it
is infected by the virus. However some viruses overwrite other programs with copies of themselves, which destroys the host program altogether. Viruses spread
when the software or document they are attached to is transferred from one computer to another using the network, a disk, file sharing, or infected e-mail
attachments.

WORMS
Computer worms are similar to viruses in that they replicate functional copies of themselves and can cause the same type of
damage. In contrast to viruses, which
require the spreading of an infected host file, worms are standalone software and do
not require a host program or human help to propagate. To spread, worms either
exploit a vulnerability on the target system or use some kind of social engineering to
trick users into executing them. A worm enters a computer through a vulnerability
in the system and takes advantage of file- transport or information-transport features
on the system, allowing it to travel
unaided.

TROJANS
A Trojan is another type of malware named after the wooden horse the Greeks used to
infiltrate Troy. It is a harmful piece of
software that looks legitimate. Users are typically tricked into loading and executing it on their systems. After it is activated, it
can achieve any number of attacks on the host, from irritating the user (popping up
windows or changing desktops) to damaging
the host (deleting files, stealing data, or activating and spreading other malware,
such as viruses). Trojans are also known to
create back doors to give malicious users access to the system.
Unlike viruses and worms, Trojans do not reproduce by infecting other files nor do they self-replicate. Trojans must spread through user interaction such as opening an
e-mail attachment or downloading and running a file from the Internet

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