Download Fundamentals of Computer Security

Fundamentals of
Computer Security
Geetika Sharma
Fall 2008
Outline
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Fundamentals of Computer Security
Security Threats and Protection Methods
Security Models and Mechanisms
Security Issues in Distributed systems
Latest Techniques
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Agent Based Approach
Grid Specific Host Based Intrusion Detection
System
Fundamentals of Computer
Security[1]
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Computer Systems
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Can be represented by:
 Subjects
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Objects
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Active entities that access objects
Passive entities that must be protected
Examples: data, hardware, software and communication links
Access Control Policy
 Describes how objects are accessed by subjects
Flow Control Policy
 Regulates the information flow between objects and
subjects
Security Threats[1]
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Interruption (availability)
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Interception
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Loss of data and denial of service
Related to secrecy
Modification and Fabrication are violations of
system integrity
Threats from Web/Network[4]
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Client Side
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What can the server do to the client?
Fool it
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Server Side
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What can the client do to the server?
 Bring it down (denial of service)
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Install or run unauthorized software, inspect/alter
files
Gain access (break-in)
Network
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Is anyone listening? (Sniffing)
Is the information genuine? Are the parties genuine?
Security Mechanisms[1]
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Authentication
 Verification
Authorization
 Extending permission
Fault Tolerance
 Sustaining faults
Encryption
 Prevents exposure of information and maintains
privacy
Auditing
 Passive form of protection
Security Models[1]
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Discretionary
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Provides separation of users and data
E.g. access control matrix
Mandatory
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Requires access control of all subjects and orders
under its control on a system wide basis
E.g. multilevel security, all subjects and objects in
the system are assigned a sensitivity label. The
labels are used as the basis for mandatory access
control decisions.
Security Issues in Distributed
Systems[1]
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Interoperability and Transparency
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Gives rise to security issues
Approaches to Implementing New Services
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Add an additional layer of software that runs on top of
the existing system to provide the new services
Redesign the system so that the new services can be
executed more efficiently in the kernel mode
Security Issues in Distributed
Systems[1]
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Client/Server Security
 A client initiates an access to an object through the
kernel
 Kernel authenticates the client and then invokes the
object server
 Implemented via Interprocess Communication at
transport layer
 Supported by secure host-to-host communications at the
network layer and node to node communication at the
link layer
 Secure distributed system consists of communicating
security servers using trusted gateway.
Security Issues in Distributed
Systems[1]
Client processes
request
response
Other OS Servers
response
Authentication
Server
Authorization
Server
Other Security
Servers
request
Trusted Secure Kernel
Client/Server Distributed Security Architecture
Latest Techniques
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Majority of information security incidents is
perpetrated by insiders i.e. internal computer users
constitute the largest threat to the computer
systems security[2].
Traditional methods (such as identification and
authentication, access restriction, etc.) do not solve
this problem
Drawbacks; among them are
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low ability of internal malicious users detection,
inability to process large amounts of information,
low productivity
Agent Approach for Security in
Distributed Systems[2]
Intelligent Security System for Computers users’
activity monitoring
 Online and off-line monitoring allowing to detect
anomalies and irregularities in user behavior.
 On-line monitoring is carried in real time, and is
used to predict user actions (use neural networks)
 Off-line monitoring is done after the user has
ended his work, and is based on the analysis of
statistical information obtained during user's work.
Agent Approach for Security in
Distributed Systems[2]
Win
98
On-line User
Agent
On-line User
Agent
Free
BSD
Dbase
Off-line User
Agent
Win
2000
On-line User
Agent
Controller
Agent
On-line User
Agent
Linux
System Architecture for Agent Based Security in Distributed systems
GHIDS: Defending Computational Grids
Against Misusing of Shared Resources [3]
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Grid Specific Host Based Intrusion Detection System
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Design
 Performance Impact
 Central Control
 Leverage Existing Software
 Configurability
 Effectiveness
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Approach/Services
 Uses Bottleneck Verification (Host)
 Detects users that go from user to super user improperly
 Monitors process creation, modification and destruction (Host)
 Monitors accessing of critical resources (Host)
 Grid User ID and Host Level ID stores when Grid services used
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Architecture
 Host and Grid level deployment
 Virtual Kernel Device created
 Grid Middleware modified
 Data Analyzer
 User Interface
References
1. Randy Chow, Theodore Jognson. Distributed Operating Systems and
Algorithms, Addison-Wesley 1997
2. Agent Approach for Providing Security in Distributed Systems;
TCSET'2006, February 28-March 4, 2006, Lviv-Slavsko, Ukraine
3. GHIDS:Defending Computational Grids Against Misusing of Shared
Resources”, Feng et all, IEEE 2006
4. www.cse.sc.edu/~farkas/csce522-2003/lectures/csce522lect22.ppt (2003)
Thanks!