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Trusted Systems and Trojan Horse

Done by : Hany Nasser

Supervised by : PhD Nabil Hamdy

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Trusted Systems

Systems used to enhance the ability to defend against intruders and malicious programs.

based on levels of security .

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Multilevel Security

When multiple categories or levels of data are defined, the requirement is referred to as multilevel security.

Typically use Mandatory Access Control.

Primary Security Goal: Confidentiality (ensuresthat information do not flow to those not cleared for that level).

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Security Goal of MLS There are security classifications or security

levels Subjects have security clearances

Objects have security classifications

Example of security levels Top Secret

Secret

Confidential

Unclassified

In this case Top Secret > Secret > Confidential > Unclassified

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Data Access Control

Through the user access control procedure (log on), a user can be identified to the system.

Associated with each user, there can be a profile that specifies permissible operations and file accesses.

The operating system can enforce rules based on the user profile.

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Data Access Control

General models of access control:

Access matrix

Access control list

Capability list

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Data Access Control

Access Matrix: Basic elements of the model

Subject

Object

Access right

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Data Access Control

Access Matrix

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Data Access Control

Access Control List: Decomposition of the matrix by columns

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Data Access Control

Access Control List For each object, An access control list lists

users and their permitted access right.

The list may contain a default or public entry.

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Data Access Control

Capability list: Decomposition of the matrix by rows

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Data Access Control

Capability list A capability ticket specifies authorized

objects and operations for a user.

Each user have a number of tickets.

Capabilities are not forgeable.

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The Concept ofTrusted Systems

Multilevel security

Definition of multiple categories or levels of data

A multilevel secure system must enforce:

No read up

No write down

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The Concept ofReference Monitor

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The Concept ofReference monitor

Reference Monitor Controlling element in the hardware and

operating system of a computer that regulates the access of subjects to objects on basis of security parameters

The monitor has access to a file (security kernel database)

The monitor enforces the security rules (no read up, no write down)

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The Concept ofReference Monitor

Properties of the Reference Monitor

Complete mediation

Isolation

Verifiability

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Trojan Horse

It is a type of malware (malicious software) designed to provide unauthorized, remote access to a user’s computer.

Trojan horses do not have the ability to replicate themselves like viruses.

With the help of Trojan, an user can get access to the Trojan horse infected computer and would be able to access the data.

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Types of Trojans

Command Shell Trojan

Email Trojan

Document Trojan

FTP Trojan

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Trojan Horse Defense

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Indications of Trojan Attack

Browser redirects to unknown pages.

Anti virus is disabled.

Strange pop ups or chat messages appear on the system.

The computer shuts down automatically.

Ctl+Alt+Del stops working.

Printer prints documents automatically.

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Examples of Trojan

Net bus

Sub seven

Y3K remote administration tool

Back Orifice

Beast

Zeus

The Black hole Exploit kit

Flashback Trojan

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How to avoid being infected ?

Do not surf or download anything from stranger website.

Do not open the unexpected attachments on emails.

We need an antivirus to protect our computer from being infected.

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References

Cryptography And Network Security, 4th

Edition by William Stallings.

Computer Security, 2nd edition by Dieter Gollman.

Specifications of multi-level security research by Daryl McCullough.

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Thank you