SERVICES, MECHANISMS, AND ATTACKS

smileybloatNetworking and Communications

Nov 20, 2013 (3 years and 10 months ago)

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1

SERVICES, MECHANISMS, AND ATTACKS

The generic name for the collection of tools designed to protect
computer data


is
computer security

(including access via network)

Collection of tools designed to protect
data during transmission
between computers in the

network is
network (internet) security

Security services

should provide:
confidentiality, authentication,
nonrepudiation, integrity
of transmitted data

Security mechanisms

should consider possible attacks on the security
features.

Three aspects of
informa
tion security
:

Security attack
: any action that compromises the security of
information owned by an organization


Security mechanism
: A mechanism that is designed to detect,
prevent, or recover from a security attack
. Many security mechanisms are
based on
cryptographic techniques

Security service:

A service that enhances the security of the data
processing systems and the information transfers of organization.
The
services are intended to counter security attacks, and the
y

make use of one
or more security m
echanisms to provide the service. They are used to
implement security policy of an organization.

Security services are to
replicate functions normally associated with physical documents.

Documents usually have: signatures, dates. They may be notarized or
witnessed, may be licensed. They may need protection from disclosure,
tampering, or destruction

Security services

are to take into account s
pecific features of
electronic documents:

1.

It is usually possible to discriminate between an original
pap
er
document
and a xerographic copy. However, an electronic
document is merely a sequence of bits; there is no difference between
the ‘original’ and any number of copies

2.

An alteration to a paper document may leave some sort
of physical evidence of the alteration. For e
xample, an erasure can
result
in a thin spot or a roughness in the surface. Altering bits in the
computer memory or in a signal leaves no physical trace


2

SERVICES, MECHANISMS, AND ATTACKS

(CONT 1)


3.

Any ‘proof’ process associated with a physical document
ty
pically depends
on the physical characteristics of that document
(e.g., the shape of a handwritten signature or an embossed notary
seal). Any such proof of authenticity of an electronic document must
be based on internal evidence present in the information

itself.

Security attacks

(Request for Comments RFC 2828
, Internet Security
Glossary,
http://www.faqs.org/rfcs/rfc2828.html

)

Threat



a potential for violation of security which exists when there
is
a circumstance, capability, action, or event that could breach security and
cause harm. That is, threat is a possi
ble danger that might exploit
vulnerability

Attack



an assault on system security that derives from an intelligent
threat; that is, an intell
igent act that is a deliberate attempt
(especially in the
sense of a method or technique)

to evade security services and violate the
security policy of a system.

Examples of attacks

1.

Gain unauthorized access to information (violate secrecy
or privacy)

2.

Imper
sonate another user either to shift responsibility or
else to use the other’s license
for the purpose of

a.

originating fraudulent information

b.

modifying legitimate information

c.

using fraudulent identity to get unauthorized access

d.

fraudulently authorizing trans
actions or endorsing them

3.

Disavow responsibility or liability for information the
cheater did originate

4.

Claim to have received from some other user information
that the cheater created (i.e. fraudulent attribution of responsibility)

5.

Claim to have sent to a

receiver (at a specified time)
information that was not sent (or was sent at a different time)

6.

Either disavow receipt of information that was in fact
received, or claim a false time of receipt

7.

Enlarge
cheater’s

legitimate license (for access,
origination,

distribution, etc.)

8.

Modify (without authority to do so) the license of others
(fraudulently enroll others, restrict or enlarge existing licenses, etc.)


3

SERVICES, MECHANISMS, AND ATTACKS

(CONT 2)


9.

Conceal the

presence of some information (a

covert
communi
cation) in other information (the overt communication)

10.

Insert self into a communication link between other users
as an active (undetected) relay point

11.

Learn who accesses which information (sources, files,
etc.) and when the accesses are made even if the in
formation itself
remains concealed (e.g., a generalization of a traffic analysis from
communication channels to data bases, software, etc.)

12.

Impeach an information integrity protocol by revealing
information the cheater is supposed to (by the terms of the p
rotocol)
keep secret

13.

Pervert the function of software, typically by adding a
covert function

14.

Undermine confidence in a protocol by causing apparent
failures in the system

15.

Prevent communication among other users, in particular,
surreptitious interference to

cause authentic communication to be
rejected as unauthentic

THE OSI

SECURITY ARCHITECTURE

OSI



Open Systems Interconnection

TCP


Transmission Control Protocol


establishes connection
between peers

IP


Internet Protocol


specifies format of transmitte
d packets,
datagrams, lower level than TCP, does not establish connections

Let’s consider ITU
-
T Recommendation X.800
-

http://www.itu.int/ITU
-
T/studygroups/com10/lan
guages/X.683_0699_Amend1.pdf


ITU
-
T



International Telecommunication Unit (ITU)
Telecommunication Standardization Sector


United Nations
-
sponsored
agency

Security Services

X.800 defines a security service as a service provided by a protocol
layer of com
municating open systems, which ensures adequate security
of the systems or of data transfers. X.800 divides these services into 5
categories and 14 specific services


4

THE OSI SECURITY ARCHITECTURE

(CONT 1)


1.

Authentication

The assurance that the communicati
ng entity is the one that it claims to
be

1.1.

Peer entity authentication

Used in association with a logical connection to provide confidence in
the identity of the entities connected

1.2.

Data
-
origin authentication

In a connectionless transfer, provides assurance t
hat the source of the
received data is as claimed

2.

Access Control

2.1.

The prevention of unauthorized use of a resource
(i.e., this
service controls who can have access to resource, under what conditions
access can occur, and what those accessing the resource ar
e allowed to
do).

3.

Data Confidentiality

The protection of data from unauthorized disclosure

3.1.

Connection confidentiality

The protection of all user data on a connection

3.2.

Connectionless confidentiality

The protection of all user data in a single data block

3.3.

Sele
ctive
-
field confidentiality

The confidentiality of selected fields within the user data on a connection
or in a single data block

3.4.

Traffic
-
flow confidentiality

The protection of information that might be derived from observation of
traffic flows

4.

Data Integr
ity

The assurance that data received are exactly as sent by an authorized
entity (i.e., contain no modification, insertion, deletion, or replay)

4.1.

Connection integrity with recovery

Provides for the integrity of all user data on a connection and detects any
modification, insertion, deletion, or replay of any data within an entire
data sequence, with recovery attempted

4.2.

Connection integrity without recovery

As above, but provides only detection without recovery


5

4.3.

Selective
-
field connection integrity

Provides for
the integrity of selected fields within the user data of a data
block transferred over a connection and takes the form of determination
of whether the selected fields have been modified, inserted, deleted, or
replayed

4.4.

Connectionless integrity

Provides for
the integrity of a single connectionless data block

4.5.

Selective
-
field connectionless integrity

Provides for the integrity of selected fields within a single connectionless
data block

5.

Nonrepudiation

Provides protection against denial by one of the entities i
nvolved in the
communication of having participated in all or part of the communication

5.1.

Norepudiation, origin

Proof that the message was sent by the specified party

5.2.

Nonrepudiation, destination

Proof that the message was received by the specified party


Als
o, there may be considered
Availability service

which protects the
system to ensure its availability


Securuty Mechanisms

X.800 defines the following mechanisms

1.

Specific security mechanisms

May be incorporated into the appropriate protocol layer in order t
o
provide some of OSI security services

1.1.

Encipherment

The use of mathematical algorithms to transform data into a form that
is not readily intelligible. The transformation and subsequent recovery of the
data depend on an algorithm and zero or more encryptio
n keys

1.2.

Digital signature

Data appended to, or a cryptographic transformation of, a data
unit
that allows a recipient
of the data unit to prove the source and integrity of the
data unit and protect against forgery

1.3.

Access control

A variety of mechanisms that

enforce access rights to resources

1.4.

Data integrity

A variety of mechanisms used to assure the integrity of a data unit or
stream of data units


6

THE OSI SECURITY ARCHITECTURE

(CONT 2)


1.5.

Authentication exchange

A mechanism intended to ensure the identity of a
n entity by means of
information exchange

1.6.

Traffic padding

The insertion of bits into gaps in a data stream to frustrate traffic
analysis attempts

1.7.

Routing control

Enables selection of a particular physically secure routes for certain
data and allows routing

changes, especially when a breach of security is
suspected

1.8.

Notarization

The use of the third trusted party to assure certain properties of a data
exchange

2.

Pervasive security mechanisms

Mechanisms,
not specific to any particular OSI security service or
pro
tocol layer

2.1.

Trusted functionality

That which is perceived to be correct with respect to some criteria
(e.g., as established by security policy)

2.2.

Security label

The marking bound to a resource (which may be a data unit) that
names or designates the security
attributes of that resource

2.3.

Event detection

Detection of security relevant events

2.4.

Security audit trail

Data collected and potentially used to facilitate a security audit, which
is independent review and examination of system records and activities

2.5.

Security

recovery

Deals with requests from mechanisms, such as event handling and
management functions, and takes recovery actions

Usage of mechanisms in services:


7

THE OSI SECURITY ARCHITECTURE

(CONT 3)


Security Attacks

X.800 and RFC 2828 distinguish passive an
d active attacks

1.

Passive attacks

Passive attacks are in the nature of eavesdropping on, or monitoring
of, transmissions

1.1.

Release of message contents



encryption is usually used to
counter attack

1.2.

Traffic analysis



if contents is closed but the opponent
cou
ld determine the location and identity of communicating hosts and
could observe the frequency and length of messages being exchanged, he
may guess the nature of the communication that was taking place

Passive attacks are very difficult to detect because th
ey do not involve
any alteration of data. However, it is feasible to prevent the success of these
attacks, usually by means of encryption.

2.

Active attacks

They involve some modification of the data stream or the creation of a
false data stream and can be su
bdivided into 4 categories

2.1.

A
Masquerade

takes place when one entity pretends to be a
different entity

2.2.

Replay

involves the passive capture of a data unit and its
subsequent retransmission to produce an unauthorized effect

2.3.

Modification of messages

simply mea
ns that some portion
of a legitimate message is altered

2.4.

The Denial of service
prevents or inhibits the normal use or
management of communication facilities


8

A MODEL FOR NETWORK SECURITY



Virus



malicious code which runs inside infected programs,
worm



independent

malicious program.



9

OUTLINE OF THE COURS
E

1.

Provides a survey of symmetric encryption, including Data
Encryption Standard (DES) and Advanced Encryption Standard (AES)

2.

Provides a survey of public
-
key algorithms, including RSA
(Rivest
-
Shamir
-
Adelm
an), digital signatures and key exchange

3.

Examines the use of cryptographic algorithms and security
protocols to provide security over networks and Internet

4.

Deals with security facilities designed to protect a computer
system from security threats, includin
g intruders, viruses, and worms;
firewalls are considered.