CSCE 201 Secure Software Development Best Practices

2 Reading This lecture: G. McGraw, Software [In]security: Software Security Zombies, 07/2011,

3 How to address software security? Do not address at all Ad-hoc evaluation Add security features after the fact Identify security vulnerabilities Test security level Incorporate security throughout of SDLC

4 Checking for Known Vulnerabilities Need tool Possible attacks and attack types How the software behaves if something goes WRONG What motivates an attacker?

5 Three Pillars of Software Security Risk Management – Business case Software Security Touchpoints – Best practices Knowledge – Tools

6 Risk Management How much effort to invest in security Consequences of security breaches Acceptable-level of security Tracking and mitigating risk throughout the full SDLC

7 Knowledge Gathering, encapsulating, and sharing security knowledge Knowledge categories: – Prescriptive knowledge – Diagnostic knowledge – Historical knowledge Applied along the SDLC

8 Touchpoints System-wide activity: from design to testing and feedback Touchpoints: 1. Code review 2. Architectural risk analysis 3. Penetration testing 4. Risk-based security testing 5. Abuse cases 6. Security requirements 7. Security operations

9 Application of Touchpoints Requirement and Use cases Architecture and Design Test Plans Code Tests and Test Results Feedback from the Field 5. Abuse cases 6. Security Requirements 2. Risk Analysis External Review 4. Risk-Based Security Tests 1. Code Review (Tools) 2. Risk Analysis 3. Penetration Testing 7. Security Operations

10 Misuse Cases Software development: making software do something – Describe features and functions – Everything goes right Need: security, performance, reliability – Service level agreement – legal binding How to model non-normative behavior in use cases? – Think like a bad guy

11 Misuse Cases Analyze system design and requirements – Assumptions – Failure of assumptions – Attack patterns Software that is used also going to be attacked What can a bad guy do and how to react to malicious use

12 Misuse Case Development Team work – software developers and security experts Identifying and documenting threats Creating anti-requirements: how the system can be abused Creating attack model – Select attack pattern relevant to the system – Include anyone who can gain access to the system

13 Application of Touchpoints Requirement and Use cases Architecture and Design Test Plans Code Tests and Test Results Feedback from the Field 5. Abuse cases 6. Security Requirements 2. Risk Analysis External Review 4. Risk-Based Security Tests 1. Code Review (Tools) 2. Risk Analysis 3. Penetration Testing 7. Security Operations

14 Software Testing Application fulfills functional requirements Dynamic, functional tests late in the SDLC Contextual information

15 Security Testing Test: finding flaws in software can be exploited by attackers Quality, reliability and security are tightly coupled Software behavior testing – Need: risk-based approach using system architecture information and attacker’s model

16 Security Testing Look for unexpected but intentional misuse of the system Must test for all potential misuse types using – Architectural risk analysis results – Abuse cases Verify that – All intended security features work (white hat) – Intentional attacks cannot compromise the system (black hat)

17 Penetration Testing Testing for negative – what must not exist in the system Difficult – how to prove “non-existence” If penetration testing does not find errors than – Can conclude that under the given circumstances no security faults occurred – Little assurance that application is immune to attacks Feel-good exercise

18 Success of Penetration Testing Depends on skill, knowledge, and experience of the tester Important! Result interpretation Disadvantages of penetration testing: – Often used as an excuse to declare victory and go home – Everyone looks good after negative testing results

19 Behavior in the Presence of Malicious Attack What happens when the software fails? – Safety critical systems Track risk over time Security relative to – Information and services protected – Skills and resources of adversaries – Cost of protection System vulnerabilities

20 Malicious Input Software: takes input Trust input? – Malformed or malicious input may lead to security compromise – What is the input? Data vs. control Attacker toolkit

21 Traditional Software Development No information security consideration Highly distributed among business units Lack of understanding of technical security risks

22 Don’t stand so close to me Best Practices – Manageable number of simple activities – Should be applied throughout the software development process Problem: – Software developers: lack of security domain knowledge  limited to functional security – Information security professionals: lack of understanding software  limited to reactive security techniques

23 Vulnerability Monitoring Identify security weaknesses Methods: – Automated tools – Human walk-through – Surveillance – Audit – Background checks

24 Red Team Organized group of people attempting to penetrate the security safeguards of the system. Assess the security of the system  future improvement Requested or permitted by the owner to perform the assessment Wide coverage: computer systems, physical resources, programming languages, operational practices, etc.

25 Next Class Midterm exam