INTRODUCTION TO INFORMATION
SECURITY
Compiled By :
Vaishali Soni
WHAT IS SECURITY?

In the context of computers, security generally means
three things:

Confidentiality


Integrity


When you ask for data, you get the “right” data
Availability


Access to systems or data is limited to authorized parties
The system or data is there when you want it
A computing system is said to be secure if it has all
three properties

Well, usually
Pillars of Security:
Confidentiality, Integrity, Availability
CONFIDENTIALITY(CIA)
: WHO IS AUTHORIZED?
INTEGRITY: IS DATA „GOOD?”
AVAILABILITY: CAN ONE ACCESS DATA WHENEVER
NEEDED?
Integrity
Confidentiality
S
Availability
S = secure
[cf. Barbara Edicott-Popovsky and Deborah Frincke, CSSE592/492, U. Washington]
BALANCING CIA
Payroll
Data
Biographical
Data
Integrity
Confidentiality
S
Sensitive
Data
Availability
S = secure
Need to balance CIA
Ex: Disconnect computer from
Internet to increase
confidentiality (availability
suffers, integrity suffers due to
lost updates)
Ex: Have extensive data checks
by different people/systems to
increase integrity (confidentiality
suffers as more people see data,
availability suffers due to locks
on data under verification)
Packet
Switch
Bridge
File
Server
Gateway
Other
Networks
[Barbara Edicott-Popovsky and Deborah Frincke, CSSE592/492, U. Washington]
Health
Data
CONFIDENTIALITY
 Use
the “need to know” basis for data access

How do we know who needs what data?
Approach: access control specifies who can access what

How do we know a user is the person she claims to be?
Need her identity and need to verify this identity
Approach: identification and authentication
 Analogously:
“need to access/use” basis for access
to physical assets

E.g., access to a computer room, use of a desktop
 Confidentiality


is:
Difficult to ensure
Easiest to assess in terms of success

Binary in nature: Yes / No
 Integrity
INTEGRITY
vs. Confidentiality

Integrity - concerned with unauthorized modification of
assets (= resources)
Confidentiality - concered with access to assets

Integrity is more difficult to measure than confidentiality
Not binary – degrees of integrity
Context-dependent - means different things in different
contexts
Could mean any subset of these asset properties:
{ precision / accuracy / currency / consistency /
meaningfulness / usefulness / ...}
 Types


of integrity—an example
A quotation from a politician
Preserve the quotation (data integrity) but mis-attribute
(origin integrity)
AVAILABILITY

We can say that an asset (resource) is available if:





Timely request response
Fair allocation of resources (no starvation!)
Fault tolerant (no total breakdown)
Easy to use in the intended way
Provides controlled concurrency (concurrency control, deadlock
control, ...)
[Pfleeger & Pfleeger]
VULNERABILITIES, THREATS, AND CONTROLS
 Understanding
Vulnerabilities, Threats, and
Controls
Vulnerability = a weakness in a security system
 Threat = circumstances that have a potential to cause harm
 Controls = means and ways to block a threat, which tries to exploit
one or more vulnerabilities


Most of the class discusses various controls and their effectiveness
[Pfleeger & Pfleeger]

Attack

= exploitation of one or more vulnerabilities by a threat; tries to
defeat controls

Attack may be:
Successful
 resulting in a breach of security, a system
penetration, etc.
 Unsuccessful
 when controls block a threat trying to exploit a
vulnerability

[Pfleeger & Pfleeger]
 Examples


Fig. 1-1 (p.6)
New Orleans disaster (Hurricane Katrina):
What were city vulnerabilities, threats, and controls
SECURITY AND RELIABILITY
Security has a lot to do with reliability
 A secure system is one you can rely on to (for example):

Keep your personal data confidential
 Allow only authorized access or modifications to resources
 Give you correct and meaningful results when you want
them

SOME TERMINOLOGY

Assets

Things we might want to protect, such as:
Hardware
 Software
 Data


Vulnerabilities
Weaknesses in a system that may be able to be exploited in
order to cause loss or harm
 e.g., a file server that doesn't authenticate its users

SOME TERMINOLOGY

Threats



A loss or harm that might befall a system
e.g., users' personal files may be revealed to the public
There are four major categories of threats:
Interception
 Interruption
 Modification
 Fabrication


When we design a system, we need to state a threat model
This is the set of threats we are undertaking to defend against
 Whom do we want to stop from doing what?

SOME TERMINOLOGY

Attack



An action which exploits a vulnerability
e.g., telling the file server you are a different user in an
attempt to read or modify their files
Control
Removing or reducing a vulnerability
 You control a vulnerability to prevent an attack and block a
threat.
 How would you control the file server vulnerability?
 Our goal: control vulnerabilities

KINDS OF THREATS
 Kinds

Interception


an asset becomes lost, unavailable, or unusable
Modification


an unauthorized party (human or not) gains access to an asset
Interruption


of threats:
an unauthorized party changes the state of an asset
Fabrication

an unauthorized party counterfeits an asset
[Pfleeger & Pfleeger]