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Prevention from Viruses:

(a) Use antivirus software to permanently remove viruses.
(b) Always scan pen drives and other secondary storage media in order to detect viruses and
safeguard your system.
(c) Frequent update your computer system.

CTM: A virus is a malicious program that damages data and files of a system and can also corrupt the file
allocation table.

2. Worms

A worm is a self-replicating program that runs independently and travels across network
connections. The characteristics of viruses and worms are more or less same, but a worm causes
more damage.

CTM: A worm is a computer program which can self-replicate and propagate over the network, with or
without human intervention, and has malicious content.

Characteristics of Worm:

(a) It replicates itself.

(b) Unlike virus, worm does not require host and it is self-contained.
(c) It spreads across networks through email, instant messaging or junk mails.
(d) Worms run independently.

The various types of Worms are:
(a) Email Worms: Worms spread through any email which contains any file attachment or link
to any infected website.

(b) Instant Messaging Worms: Worms spread through instant messaging across the network
by sending mails to infected website.
(c) Internet Worms: The infected worm will use the contact list of the user’s chat-room profile
or instant-message program to send links to infected websites. These are not as effective as
email worms as the recipient needs to accept the message and click the link. The users of
the particular program are affected by it.
(d) File Sharing Network Worms: These types of worms are downloaded along with the
required files downloaded by the user. A user is not aware about this worm and, therefore,
when the user downloads any file, the worm will copy itself into a shared folder with an
Computer Science with Python–XII 8.44 Damage caused by Worms:
unassuming name. When another user on the network downloads files from the shared
folder, the worm gets downloaded on their system also. In this way, the worm copies itself
and repeats the process. In 2004, a worm called “Phatbot” infected millions of computers in
this way and had the ability to steal personal information, including credit card details, and
send spam on a large scale.

(a) A worm may corrupt the files on the host computer.
(b) It may affect communication between the host and other systems.