What is virus and its types

What is virus and its types?

VIRUS Full form: Vital Information Under Seize.

Meaning of full form:
Vital means Important

Information means important data that is very important for a person

Under Seize means possessed by someone or steal by someone.

A virus is a man-made computer program that infects a file or program on
our computers. It replicates or spreads itself by infecting other programs on the same computer.

A wormA worm is also a man-made program that replicates itself. A worm
can spread itself automatically to other computers.

Viruses and worms can infect network servers, desktop computers, laptops,
tablets and mobile 'phones... they pose one of the most serious Internet
security risks, reaching our PCs from email, web sites, downloaded files and
loadable media, such as USBs, CD-ROMs and DVDs.

There are thousands of different kinds of viruses but they form distinct groups.

Program or File Virus--:> Infects executables (other programs, with
affixes such as EXE, BIN, COM, SYS)

Boot sector Virus--:> Infects boot sectors on hard and floppy disks

Multipartite Virus--:> A hybrid of a program and boot sector virus

Macro Virus--:> Triggers on a command in Microsoft Office ( Commonly affects Word & Excel)
Stealth Virus--:> Uses various tactics to avoid detection.
Polymorphic Virus--:> Uses various tactics to avoid detection.

Now one more important thing according to examination point of view i.e Trojan Horse

Trojan horse is categorized in Virus, but actually it is not a 100% true Virus and do not replicate. It is a malicious program, it is downloaded free with the software that is downloaded from the online sites. Mostly software are malicious free but some are not.

And we do not ignore free things ;)

A Trojan horse can capture information from our system > such as user names and passwords could allow a malicious hacker to remotely control our computer.