Overview of Security Dr. Sriram Chellappan [email protected] These slides are available at BlackBoard

Overview of SecurityOverview of Security

Dr. Sriram [email protected]

These slides are available at BlackBoard

OverviewOverview

Security Definitions Security threats and attacks Security Services Operational Issues

The DefinitionThe Definition Security is a state of well-being of information and

infrastructures in which the possibility of successful yet undetected theft, tampering, and disruption of information and services is kept low or tolerable

Security rests on confidentiality, authenticity, integrity, availability, non-repudiation

In OS termsIn OS terms Operating System Computer security

– Addresses the issue of preventing unauthorized access to resources and information maintained by computers

– Encompasses the following issues:

• Guaranteeing the privacy and integrity of sensitive data

• Restricting the use of computer resources

• Providing resilience against malicious attempts to incapacitate the system

– Employs mechanisms that shield resources such as hardware and operating system services from attack

The Basic ComponentsThe Basic Components Confidentiality is the concealment of information or

resources. Authenticity is the identification and assurance of the origin

of information. Related to privacy

Integrity refers to the trustworthiness of data or resources in terms of preventing improper and unauthorized changes.

Availability refers to the ability to use the information or resource desired.

Non-repudiation means that it can be verified that the sender and the recipient were, in fact, the parties who claimed to send/ receive a particular message, and the message sent/ received were the same

Security Threats and AttacksSecurity Threats and Attacks A threat is a potential violation of security.

Flaws in design, implementation, and operation. An attack is any action that violates security.

Active adversary. A threat is typically a precursor to an attack

Eavesdropping - Message Eavesdropping - Message Interception (Attack on Interception (Attack on

Confidentiality)Confidentiality) Unauthorized access to information Packet sniffers and wiretappers Illicit copying of files and programs

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Eavesdropper

Techniques to Enforce Techniques to Enforce ConfidentialityConfidentiality

Symmetric key distribution What are the challenges

How to secure transmit the symmetric keys Key revocation after a certain point in time Protect the key from being lost

Latest technique to solve this problem Asymmetric keys

Integrity Attack - Tampering Integrity Attack - Tampering With MessagesWith Messages

Stop the flow of the message Delay and optionally modify the message Release the message again

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Perpetrator

Techniques to Enforce IntegrityTechniques to Enforce Integrity

Message Authentication Codes Accomplished using hash functions That are collision resistant and have one-way

property

Authenticity Attack - FabricationAuthenticity Attack - Fabrication

Unauthorized assumption of other’s identity Generate and distribute objects under this identity

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Masquerader: from S

Techniques to Enforce Techniques to Enforce AuthenticationAuthentication

Standard Techniques are passwords Easy to be captured by adversary Easy to be guessed by adversary

Evolving techniques Biometrics One time password generator Expand sample space of secret – password mapping

Access control mechanisms Kerberos – A well known authentication technique

What is Kerberos?What is Kerberos? Developed by MIT Shared secret-based strong 3rd party authentication Provides single sign-on capability Passwords never sent across network

And now – the players…

Susan

KeyDistribution

Center

TicketGrantingService

Authen-TicationService

XYZ Service

Susan’sDesktop

Computer

Think “Kerberos Server” and don’t let yourself get mired in terminology.

Susan

KeyDistribution

Center



XYZ Service

Susan’sDesktop

Computer

Represents something requiring Kerberos authentication (web server, ftp server, ssh server, etc…)

Susan’sDesktop

ComputerSusan

KeyDistribution

Center



XYZ Service

“I’d like to be allowed to get tickets from the Ticket Granting Server, please.

Susan’sDesktop

ComputerSusan

KeyDistribution

Center



XYZ Service“Okay. I locked this box with your secret password. If you can unlock it, you can use its contents to access my Ticket Granting Service.”

Susan’sDesktop

ComputerSusan

KeyDistribution

Center



myPassword

XYZ Service

TGT

TGT

Because Susan was able to open the box (decrypt a message) from the Authentication Service, she is now the owner of a shiny “Ticket-Granting Ticket”.

The Ticket-Granting Ticket (TGT) must be presented to the Ticket Granting Service in order to acquire “service tickets” for use with services requiring Kerberos authentication.

The TGT contains no password information.

Susan’sDesktop

ComputerSusan

KeyDistribution

Center



XYZ Service

“Let me prove I am Susan to XYZ Service.

Here’s a copy of my TGT!”

use XYZ

TGTTGT

Susan’sDesktop

ComputerSusan

KeyDistribution

Center



XYZ Service

TGT

Hey XYZ: Susan is Susan.

CONFIRMED: TGS

You’re Susan.

Here, take this.

Susan’sDesktop

ComputerSusan

KeyDistribution

Center



XYZ Service

TGTHey XYZ:

Susan is Susan.CONFIRMED: TGS

I’m Susan. I’ll prove it. Here’s a copy of my legit service ticket for

XYZ.


CONFIRMED: TGS

Susan’sDesktop

ComputerSusan

KeyDistribution

Center



XYZ Service

TGTHey XYZ:



CONFIRMED: TGS

That’s Susan alright. Let me determine if she

is authorized to use me.

Authorization checks are performed by the XYZ service…

Just because Susan has authenticated herself does not inherently mean she is authorized to make use of the XYZ service.

One remaining note:

Tickets (your TGT as well as service-specific tickets) have expiration dates configured by your local system administrator(s). An expired ticket is unusable.

Until a ticket’s expiration, it may be used repeatedly.

Susan’sDesktop

ComputerSusan

KeyDistribution

Center



XYZ Service

TGTHey XYZ:


ME AGAIN! I’ll prove it. Here’s

another copy of my legit service ticket

for XYZ.


CONFIRMED: TGS

use XYZ

Susan’sDesktop

ComputerSusan

KeyDistribution

Center



XYZ Service

TGTHey XYZ:



CONFIRMED: TGS

That’s Susan… again. Let me determine if she

is authorized to use me.

Attack on AvailabilityAttack on Availability Destroy hardware (cutting fiber) or software Corrupt packets in transit

Blatant denial of service (DoS): Crashing the server Overwhelm the server (use up its resource)

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Techniques to Enforce Techniques to Enforce AvailabilityAvailability

Think of an example Standard technique is almost always redundancy –

Also called over-provisioning Can be counter-productive sometimes

Think how

Impact of AttacksImpact of Attacks Economic impacts Societal impacts Military impacts

All attacks can be related and are dangerous!

Some trade-offs w.r.t. securitySome trade-offs w.r.t. security

Availability vs. Privacy Confidentiality vs. Power management Privacy vs. Delay Bandwidth vs. Privacy

Security Policy and MechanismSecurity Policy and Mechanism Policy: a statement of what is, and is not allowed. Mechanism: a procedure, tool, or method of enforcing a

policy. Security mechanisms implement functions that help

prevent, detect, and respond to recovery from security attacks.

Security functions are typically made available to users as a set of security services through APIs or integrated interfaces.

Cryptography underlies many security mechanisms.

Operational IssuesOperational Issues

Cost-Benefit Analysis Risk Analysis Laws and Customs

Human IssuesHuman Issues Organizational Problems People Problems

Proprietary and Open-Source SecurityProprietary and Open-Source Security Advantages of open-source security applications

Interoperability Open-source applications tend to implement standards and

protocols that many developers include in their products. An application’s source code is available for extensive testing

and debugging by the community at large Weaknesses of proprietary security

Nondisclosure The number of collaborative users that can search for security

flaws and contribute to the overall security of the application is limited

Proprietary systems, however, can be equally as secure as open-source systems

Documents

Overview of Security Dr. Sriram Chellappan [email protected] These slides are available at BlackBoard