Software Security: Intro and Syllabus

• Course introduction and syllabus discussion led by Dr. Nada Hany Sherief

Agenda

• Course introduction and syllabus discussion to cover course overview, learning objectives, prerequisites, grading policy, schedule, and policies
• Software Security Concepts to cover terminology (threats, vulnerabilities, attacks), security goals(confidentiality, integrity, availability), software security definition, and security models

Learning Objectives:

• Understand software security concepts
• Understand software security problems and threats
• Experiment with and measure software security through estimation and metrics
• Understand secure software architecture and assurance
• Apply secure software development life cycle
• Experiment with and apply software security and testing.

Course Overview

• Course includes introduction and syllabus, security concepts, problems, threats, metrics, and estimation
• There is a 7th week assessment
• Secure Software Architecture and Assurance will be reviewed
• Focus on Secure Software Development Process and Testing
• There is a 12th Week Assessment
• Case studies on implementing security testing and security
• Project Presentations

Course Grading System

• 12th week: 10 marks on exam and 10 marks on section
• 7th week: 20 marks on exam and 10 marks on section
• Final Exam: 40 marks
• Continuous Assessment: 10 marks on Quizzes and Assignments

Lecturer Contact Info

• E-mail: [email protected]
• Office hours: Sunday 10:00 – 12:00 and Wednesday 10:00 – 12:00

Course Policies

• Attendance is taken every class
• Excuses for absence must be presented within one week after
• Students check Google Classroom for lecture notes
• Submitted work must be original; violations of Plagiarism and/or collusion will result in disciplinary action
• All group members attend the final project discussion with the TA, Ms. Salma Yasser (absence = penalty)
• Late submissions= penalty
• No coursework accepted after the 15th week

Important Terminology

• A threat is a potential occurrence, malicious or otherwise, that could harm an asset
• A threat is any bad thing that can happen to assets
• An attack is an action that exploits a vulnerability or enacts a threat
• Attacks include sending malicious input to an application or flooding a network to deny service
• A threat is a potential event that can adversely affect an asset, whereas a successful attack exploits system vulnerabilities
• A vulnerability is a weakness that makes a threat possible due to poor design, configuration mistakes, or insecure coding techniques
• Weak input validation is an example of an application layer vulnerability, which can result in input attacks

Software Security vs Application Security

• Software Security defends against exploits by building secure software
• Application Security defends against exploits post-deployment

Security Goals

• CIA Triad: Confidentiality, Integrity, Availability

Confidentiality

• Only authorized individuals can access information
• Government agencies must protect classified documents
• Nuclear weapon designs qualify
• Critical military plans are examples
• There are sensitive diplomatic communications
• There is advanced technology information and classified research data

Confidentiality Measures

• Measures to prevent the unauthorized disclosure of classified documents
• Classification Systems: Guidelines for classifying documents based on sensitivity
• Access Controls: Limits access to authorized personnel
• Encryption: Protects sensitve data from unauthorized access
• Secure Storage: Store sensitive documents in secure locations
• Personnel Security: Background checks for personnel who handle classified information
• Incident Response: A plan to respond to security breaches involving classified information

Integrity

• Information should be accurate and has not been modified or tampered with
• Data integrity is crucial in financial systems to ensure the accuracy, reliability, and consistency of financial data
• Verify account balances are accurate and reflect all transactions
• Account data is consistent across different systems and databases

Integrity Measures

• User access controls restrict access to systems to only those that require access
• File permissions are core to the security model used by Linux systems and determine who can access files and directories
• There are eight possible numbers to expresses the file permissions in Linux based systems
• Option 0 is for no permissions
• Option 1 is for execute
• Option 2 is for write
• Option 3 is for execute and write
• Option 4 is for read
• Option 5 is for execute and read
• Option 6 is for write and read
• Option 7 is for execute, write, and read
• Version control prevents erroneous changes or accidental deletion by authorized users
• A checksum is like a unique fingerprint of a file and it is used to verify whether two files are identical
• Each run checksum creates a number string for each file
• Even if one byte of data is altered or corrupted, that string will change
• Backups or redundancies restore affected data to its correct state

Availability

• Users can access and use resources when they need them, accessible, usable, and uninterrupted
• E-commerce websites can be used without interruptions
• Banking systems provides the ability to access accounts and perform transactions at any time
• Healthcare systems can access medical records and information when needed

Availability Measures

• Redundancy: Hardware, software, and data redundancy
• Fault Tolerance: Includes error detection and correction and automatic failover
• Load Balancing: Distributes workload across multiple servers or components
• Firewalls protect systems from unauthorized access and prevent DoS attacks

Security Models: Bell-LaPadula

• Aims to protect confidentiality built on restricting information flow
• For instance sensitive information must be only accessible to authorized personnel in a military database
• David Elliot Bell and Leonard J. LaPadula invented the model
• Bell-LaPadula is used to maintain the confidentiality of security.
• The classification of Subjects (Users) and Objects (Files) are organized in a non-discretionary fashion, with respect to different layers of secrecy
• Bell-LaPadula has main 3 rules
• Simple Confidentiality Rule prevents reading above your clearance
• Star Confidentiality Rule prevents writing below your clearance
• Strong Star Confidentiality Rule prevents reading above and writing below your clearance

Bell-LaPadula Model Rules

• SIMPLE CONFIDENTIALITY RULE:
  • Subject can only read the files on the Same Layer of Secrecy and the Lower Layer of Secrecy but not the Upper Layer of Secrecy, due to which this rule is NO READ-UP
• STAR CONFIDENTIALITY RULE:
  • Subject can only write the files on the Same Layer of Secrecy and the Upper Layer of Secrecy but not the Lower Layer of Secrecy, due to which this rule is NO WRITE-DOWN
• STRONG STAR CONFIDENTIALITY RULE:
  • Strong Star Confidentiality Rule is highly secured and the Subject can read and write the files on the Same Layer of Secrecy only and not the Upper Layer of Secrecy or the Lower Layer of Secrecy, write up down isn't possible here

Applying the Bell-LaPadula Model in a University

• In this scenario, the university is implementing a new online learning platform which stores sensitive student data
• This data must be protected from unauthorized access and disclosure

Define Security Levels

• Top Secret: Sensitive administrative data (faculty salaries and budget information)
• Secret: Student grades, transcripts, and personal information
• Confidential: Course materials, announcements, and general information
• Unclassified: Publicly accessible information (news and events)

Assign Security Labels:

• Subjects: Students, faculty, and administrators
• Objects: Files, documents, and databases containing sensitive information

Enforce the Bell-LaPadula Rules:

• Simple Confidentiality Rule (No Read-Up)
  • Students can only access information at their own security level or below.
  • Faculty and staff can access information at their own security level or below

Implementing the Scenario: Student Access

• Students are subjects
• Grades and transcripts comprise the objects
• Security levels are classified into Secret, Confidential, and Unclassified labels
• Students can only read files at their current security level

Implementing the Scenario: Faculty Access

• Faculty are the subjects
• Student grades and administrative data are the objects
• The corresponding security levels are Secret, Confidential, and Unclassified labels
• Faculty can read files at their own security level or below their level

Implementing the Scenario: Administrator Access

• Administrators are the subjects
• All levels of data represent the objects
• Security Levels: Top Secret, Secret, Confidential,Unclassified
• Administrators can read files at all security levels

Implementing the Scenario: Enforce the Bell-LaPadula Rules

• Star Confidentiality Rule (No Write-Down):
  • Students cannot write to files at lower security levels, so a student cannot change his or her grades
  • Administrators can write to files at their own security level or higher.
  • Faculty can write to files at their own security level and higher

Scenario 2: Faculty Access

• Faculty can write to files at their own security level
• Faculty normally cannot write to files at higher security levels like
  • Department Financial Data (Restricted Write Up) can't be modified ###Implementing the Scenario: Administrator Access Administrators must adhere to the Bell-LaPadula rules to prevent unauthorized disclosure

Enforce the Bell-LaPadula Rules

The Strong Star Confidentiality Rule is generally not applicable in the classroom setting because it is too restrictive

Example Scenarios

• Student Access: Students cannot access other students' grades or sensitive administrative data
• Faculty Access: Staff has access to course rosters and grading policies
• Administrator Access: Although administrative staff has access to grades, they must prevent unauthorized

Advantages of Bell-LaPadula Model

• Helps to ensure that security measures are consistent and effective
• Clearly defines the goal of confidentiality and provides specific rules for achieving it
• Can be applied to a wide range of systems and applications, from military databases to commercial software

Disadvantages of Bell-LaPadula Model

• Can be complex to implement, especially for organizations unfamiliar with security models
• Star rule can be restrictive when data needs to flow downward in a hierarchical structure
• Rules can hinder collaboration between users at different security levels because research may require that the classified level of data must be shared with those at a lower level