This document provides an overview of operating system security. It discusses the key components and functions of an operating system including multitasking, resource management, user interfaces, and more. It then examines the security environment of an operating system including services, files, memory, authentication, authorization, and vulnerabilities. Finally, it outlines best practices for securing an operating system such as installing only necessary software, configuring users and permissions properly, applying patches and updates, and performing regular security monitoring, backups and testing.

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O I S
S T

2. O I S
S T

3. Operating System Overview
• Operating system: collection
of programs that allows user
to operate computer
hardware
• Three layers:
– Inner layer, computer
hardware
– Middle layer, operating
system
– Outer layer, different
software

4. Operating System Overview
• Key functions of an operating system:
– Multitasking, multi sharing
– Computer resource management
– Controls the flow of activities
– Provides a user interface
– Administers user actions and accounts
– Runs software utilities and programs
– Enforce security measures
– Schedule jobs
– Provide tools to configure the operating system
and hardware

5. The OS Security Environment
• A compromised OS can
compromise a database
environment
• Physically protect the
computer running the OS
(padlocks, chain locks,
guards, cameras)
• Model:
– Bank building (operating
system)
– Safe (database)
– Money (data)

6. The Components of an OS Security Environment
• Used as access points
to the database
• Three components:
– Services
– Files
– Memory

7. Services
• Main component of operating system security
environment
• Used to gain access to the OS and its features
• Include
– User authentication
– Remote access
– Administration tasks
– Password policies

8. Files
• Common threats:
– File permission
– File sharing
• Files must be protected from unauthorized
reading and writing actions
• Data resides in files; protecting files
protects data

9. File Permissions
• Read, write, and execute privileges
• In Windows:
– Change permission on the Security tab on a
file’s Properties dialog box
– Allow indicates grant; Deny indicates revoke

10. Sharing Files
• Naturally leads to security risks and threats
• Peer-to-peer programs: allow users to share files
over the Internet
• Reasons for blocking file sharing:
– Malicious code
– Adware and spyware
– Privacy and confidentiality
– Pornography
– Copyright issues

11. Memory
• Hardware memory available on the system can be
corrupted by badly written software
• Can harm data integrity
• Two options:
– Stop using the program
– Apply a patch (service pack) to fix it

12. Authentication
• Authentication:
– Verifies user identity
– Permits access to the operating system
• Physical authentication:
– Allows physical entrance to company property
– Magnetic cards and biometric measures
• Digital authentication: verifies user identity by
digital means

13. Authorization
• Process that decides whether users are
permitted to perform the functions they
request
• Authorization is not performed until the
user is authenticated
• Deals with privileges and rights

14. User Administration
• Create user accounts
• Set password policies
• Grant privileges to users
• Best practices:
– Use a consistent naming convention
– Always provide a password to an account and
force the user to change it at the first logon
– Protect passwords
– Do not use default passwords

15. Vulnerabilities of OS
• Top vulnerabilities to Windows systems:
– Internet Information Services (IIS)
– Microsoft SQL Server (MSSQL)
– Windows Authentication
– Internet Explorer (IE)
– Windows Remote Access Services
– Microsoft Data Access Components (MDAC)
– Windows Scripting Host (WSH)
– Microsoft Outlook and Outlook Express
– Windows Peer-to-Peer File Sharing (P2P)
– Simple Network Management Protocol (SNMP)

16. NIST Approach Phases
• Planning
• Installation
• Configuration
• Update
• Maintenance
• Consider the OS layered model, each layer
needs to be properly secured, and it may be
attack from layers bellow

17. OS Layered Model
User Space
Services / Hypervisor
System Calls
Device Drivers / Hardware Abstraction Layer (HAL)
Kernel / BIOS
Instruction Set Architecture
Hardware
Physical World

18. Hardening the OS
• Default OS configurations are for ease of use
• Measures have to be done at all stages
– Installing and patching
– Configuring
• Remove unnecessary applications, services and protocols
• Users, groups, controls and privileges
– Install additional software (anti-virus, firewall, intrusion
detection system, etc.)
– Test Security

19. Installing and Patching
• Installation
– Machines should not connect to network until secured
• However removable media may be infected as well
– Limited network (firewall) is acceptable, ideally:
• No inbound connections
• Only out to certain key sites
– Install only required services and drivers (from trusted sources)
– Set up automatic updates (only if update time is not an issue)
• Booting
– Protect BIOS changes with password
– Disable some bootable media
– Cryptographic hard drives? Pros and Cons

20. Automatic Updates

21. Remove Unnecessary Support
• Software have vulnerabilities, hence more software
= more vulnerabilities
• Better to not install it at all
– Uninstallers sometimes fail to clean all dependency
– Disabled software may be enabled by an attacker upon
control acquisition
• Disabling can be done via msconfig command
(Windows), yast or equivalent (Linux) or Control
Panel (Windows / Linux)

22. Configure Authentication
• Define user types and privileges
– Admin (ideally only temporary)
– Normal
– Limited
• Authentication
– Force default password change
– Password definition
– Password lifespan
• Remove or disable old accounts
• Allow for remote connections?

23. Additional Security and Testing
• Anti-virus
• Firewalls, IDS, IPS
• White list
– If attackers manage to install a program what will
happen?
• Run some test cases which attempt to break
security (stress testing), good hackers make a
lot of money here

24. Application Security
• Configure applications properly
• Use encryption when possible as seen earlier
– For storing
– For transmit (SSH connections)
• Limit privileges as with users
– Remember what we have said about security in Android,
Blackberry, and iPhone
• Applications may provide backdoors if not
configured properly

25. Maintenance
• Now that system is set, keep it secure
• This involves
– Monitoring and analyzing logging information
– Performing regular backups
– Recovering from security compromises
– Regular testing of security
– Patch, update, and revise critical software

26. Logging
• Keep a record of important events in the
computer
• Problems
– Need to make sure to have enough space
– Manual analysis is hard, so these logs should
contain a format such that a program (e.g. in
Perl) can parse messages

27. Data Backup
• Backup is the act of creating copies of information
such that it may be recovered
• Archive is to keep these backups for a long period of
time in order to meet some legal aspects
• Should the backup be kept online or offline?
– Online makes easier access, faster recover
– Offline is more secure, harder to recover
– Why not both?: Users should keep their own offline
backups, in case online backup gets removed
• Data may be lost accidentally (hardware failures,
human mistake) or intentionally

28. Windows Security
• Use automatic updates specially for
– Windows
– Adobe Acrobat Reader and Flash Plugin
– Java
• Users are defined with a Security ID (SID) and
information such as passwords may be stored at
Security Account Manager (SAM)
• System restore
• User Account Control to treat users with admin only
as admin when required, otherwise as normal
(Vista and later)

29. Windows Registry
• Hard to maintain
• Easy to access
• May use a specific application hiding complex
information from administrator
• May use regedit to see everything
– Useful to have an application that queues and
monitors registry changes, such that they need to
get approved before proceeding

30. Other Windows Security
• Anti-virus
• Anti-spyware
• Personal firewall
• Encrypting File Systems
– Local Security Policy
• BitLocker: full disk encryption with AES
• More on Control Panel System Security
• Microsoft Baseline Security Analyzer
– Checks for minimal recommended requirements in a system
– Its free
– Shavlik NetChk Limited for legacy

31. Virtualization
• Virtualization: defines an isomorphism that maps a
virtual guest system to a physical host
• Adds another degree of freedom by enabling
multiple resource managers and controlled sharing.
– Adds a level of indirection
• Can virtualize a single resource (DRAM, Disks) or an
entire system (machine).
– may create one or more virtual objects.
• Virtual Machine: Add virtualization layer which
transforms the physical machine into the desired
virtual architecture.

32. Some Virtual Machines
• Oracle VirtualBox
• Microsoft Virtual PC (formerly Virtual PC)
• VMware
• Xen Hypervisor
• Parallel Desktop (popular on MAC)

33. Questions ?
email : rameshogania@gmail.com
Gsm : 9969 37 44 37