Why?:to protect the computing
system and protect the data that they
store and access
Security attacks :- actions that
comprises the computer security
Security mechanisms:-tools such as
algorithms, protocols designed to
detect ,prevent or recover from a
Security services :-specific kind of
protection to the system resources
• Threat potential violation of
security and also causes harm.
• Vulnerability a weakness that is
Passive attack:getting information from the
system ,but it does not affect the system.
analyzing the traffic to find the nature of
difficult to detect as they do not involve
alteration of the data
Hence better to Prevent rather than Detection
Active Attack: tries to alter the system
resources or affect its operations.
replay(capture events and replay)
Modifications of messages
Denial of services
“Difficult to prevent but can be detected and
• privacy of user
» eg.pin(personal identification number) of
atm,credit card, login id’s, pass codes
tracking of users habits and actions
Cookies(cannot install malware) and spam mails are
used for attacking
Attacks on computer hardware
• Natural calamities such as Floods,
Earthquakes, power fluctuations.
• Destructive actions of burglars or people
Attacks on software
to harm the data stored and programs in
Executables files:- programs written to do
harm rather than good
malicious software :-a software code
included into the system which is harmful in
Hacking:-intruding into another computer or
network to perform an illegal act
A software program which is Destructive in nature.
can attach itself to other healthy programs.
replicates itself and thus can spread across a network
Infects an executable file or program
Cannot infect write protect disks , hardware,
How dies it harm?
• Corrupt or delete data, change functionality of software ,
erase everything on the hard disk, degrade the system
E mail attachment, downloads on internet.
Eg. I love you, melissa,Brain, anna kournikova……….
Java scripts ,java applets and
• Java applets :- it can be part of a web
page and executed by the Java
Virtual Machine executed by browsers
for many platforms, including Microsoft
Windows ,Unix, Linux etc.
• ActiveX controls:- similar to java
applets but do not have security
• Java scripts:-a scripting
language commonly implemented as
part of a web browser in order to
create enhanced user interfaces and
• Self replicating software that uses network
and security holes
• it scans the network of a system and copies
itself and then starts replicating from there.
• Worm and virus are different
• Consumes the resources like bandwidth of
computer and makes it slow.
E.g. nimda(multiple infectious virus),
code red (Chinese),
• It is a destructive program that
masquerade as useful program.
• The reason behind the name is
the Greek soldiers who
reached the city of troy by
hiding in the wooden horse.
Similarly games, software etc.
can corrupt Data, Programs or