Antivirus

Antivirus
Q. What is an antivirus?
Ans. Anti-virus software is a program or set of programs that are designed to prevent, search
for, detect, and remove software viruses, and other malicious software like worms, trojans,
adware, and more.
These tools are critical for users to have installed and up-to-date because a computer without
anti-virus software installed will be infected within minutes of connecting to the internet. The
bombardment is constant, with anti-virus companies update their detection tools constantly to
deal with the more than 60,000 new pieces of malware created daily.
There are several different companies that build and offer anti-virus software and what each
offers can vary but all perform some basic functions:
 Scan specific files or directories for any malware or known malicious patterns
 Allow you to schedule scans to automatically run for you
 Allow you to initiate a scan of a specific file or of your computer, or of a CD or flash drive
at any time.
 Remove any malicious code detected –sometimes you will be notified of an infection and
asked if you want to clean the file, other programs will automatically do this behind the
scenes.
 Show you the ‘health’ of your computer


Types of Antivirus:

 Avast Antivirus
 AVG Antivirus
 Norton Antivirus
 Digital Patrol
 Norman Antivirus
 Clam Antivirus
 Kaspersky Antivirus
 Trend Micro Antivirus




Computer Virus- A Deadly Infection
A computer virus is a malware program that, when executed, replicates by inserting copies of itself (possibly
modified) into other computer programs, data files, or the boot sector of the hard drive; when this replication
succeeds, the affected areas are then said to be "infected". Viruses often perform some type of harmful activity on
infected hosts, such as stealing hard disk space or CPU time, accessing private information, corrupting data,
displaying political or humorous messages on the user's screen, spamming their contacts, or logging their
keystrokes. However, not all viruses carry a destructive payload or attempt to hide themselves—the defining
characteristic of viruses is that they are self-replicating computer programs which install themselves without the
user's consent.
Computer viruses are, like their biological namesake, programs that infect your system and multiply. Viruses have
many symptoms: some can simply slow down your computer whilst others can have more severe effects like
moving documents and/or deletion of documents or programs. No matter the severity of the virus and its
symptoms they should be dealt with by an up-to-date anti-virus program and security software, as systems with
out-of-date protection are more susceptible and at risk.
Computer viruses are most commonly passed through interaction over the internet, whether they are attached to
(or are disguised as) downloaded files or emails sent from friends with already compromised systems. Viruses can
be passed from computer to computer without the owners knowing they are passing them along.
There are 3 basic types of viruses: Trojan Horses, Worms and Email Viruses.
Trojan Horses – A Trojan – named after the Greek army’s tactic of hiding their soldiers in a giant wooden horse
that was sent as a gift to the city of Troy (In Homer’s epic Illiad) – disguises itself as a document or file of interest,
e.g. a sound-bite or song for a music lover, a new patch for an MMO or game for gamers or a picture/video. These
viruses do not multiply but rather make your computer’s protection weaker and thus makes your system more
susceptible to viruses and other kinds of malicious software.
Worms – The Worm-style of virus is a program that, once inside your system, multiplies and scans for flaws or
loop-holes in your security systems and protection. The Worm-style virus attempts to spread itself through a large
network by taking advantage of the loop-holes and flaws that it finds or sending itself through the intranet of the
network to other computers.
Email Viruses – Email viruses use (as suggested by the name) emails to send itself to other computers and spread
itself, they often forward themselves from infected computers.
Prevention and protection from these types of viruses are simple; usually an up-to-date anti-virus software and
security program is all that is needed. Recommended companies that supply anti-virus software and other
protection/security programs are AVG, Symantec, Avast! And Sophos.
Anti-Virus software is a useful tool against viruses, which is a given. Having been specifically designed to combat
the viruses, any good A-V software will regularly scan, at routine intervals that you can set, your computer, stored
files and hard drives for viruses. Most decent A-V software will give you several options, allowing you to enact a
scan at your discretion, the depth of the scan and connects you, through the software and internet, to a database
which stores data on the viruses found on a fellow A-V user’s computer. Another feature most A-V software gives
is the automatic scan of any files you download through your web browser, or the option to scan any file you
already have downloaded on to your system. Downloading from the internet is risky, you can never be sure of
where the file is coming from. Viruses, as stated above, can be, and often are, disguised as files of interest for
certain people to fall foul of.
As well as receiving viruses through an email system, which are usually disguised as a file attached to an email
from an unknown sender or random contact, there are other problems associated with email systems. These
problems are things such as: files not attaching to emails, mail from misrepresented or unknown users and
inappropriate content in junk-mail.

Commonly Known Viruses:

Boot viruses
Since nobody uses floppy disks anymore, these types of computer virus are left to infect only the master boot
records of the hard disk. The boot record program loads the operating system in the memory at startup. These
viruses replace the boot record and move it to a different part of the hard disk, or simply overwrite it. As you can
imagine, once you start your operating system, it loads into memory, along with the virus. Once the virus is in the
memory, it is free to do whatever it was programmed to do. To avoid loading the boot record viruses into memory,
you must boot your operating system from another source (another hard drive or a bootable CD/DVD).
Program viruses
These types of computer virus will infect only executable files (with extensions like .BIN, .COM, .EXE, .OVL, .DRV,
and .SYS). Once executed, these programs load into memory, along with the virus contained within them. Once in
the memory, the scenario repeats – the virus is free to act and infect other files or simply deliver its payload. These
viruses are friendlier than boot viruses and can be removed a lot easier.
Multipartite viruses
These computer viruses are hybrids, derived from boot viruses and program viruses. They infect executable files,
just like the program viruses but, once the executable is executed, it infects the master boot records. The scenario
is similar to the boot virus’s one: once you boot your operating system, the virus is loaded into the memory, from
where it is free to infect other programs and replicate itself, ultimately delivering the payload.
Stealth viruses
These viruses are specialized in avoiding detection and will use a number of techniques to do so. Most of them
simply redirect the hard disk head, forcing it to read another memory sector instead of their own. Some of them
also alter the reading of the file size shown when listing the directory. These types of computer virus are very hard
to find by humans, but antivirus software is specially designed to track them down and erase them.
Polymorphic viruses
The polymorphic viruses will always change their source code from one infection to another. Each infection is
different, and this makes detection very hard. However, detection is still possible, depending on the antivirus.
Macro viruses
This virus is relatively new and it infects macros within a template or document. When you open a word processing
document, it activates the virus. The virus infects the Normal.dot template, which is a general file used by all the
documents. So, whenever you open an uninfected document, by referring to the Normal.dot file, it gets infected as
well. This infection can only spread if infected documents are opened on another machine.
Active X viruses
Most people do not know how to configure ActiveX and Java controls, unconsciously leaving a security hole. Applets
are then allowed to run freely on the machine, delivering all ActiveX viruses. By simply turning off some ActiveX
and Java controls in the browser, a user can efficiently protect their PC from this type of computer virus.

Types of Viruses:
 Acme
 Ada
 Agena
 AGI-Plan
 AI
 Creeper
 Eliza
 Elk Cloner