Computer Security.ppt
- 1. CMSC 414 Computer and Network Security Jonathan Katz
- 2. Introduction and overview What is computer/network security? Why is it important? Course philosophy and goals Course organization and information High-level overview of topics A broad perspective on “computer security”
- 3. “Security” Most of computer science is concerned with achieving desired behavior Security is concerned with preventing undesired behavior – Different way of thinking! – An enemy/opponent/hacker/adversary who is actively and maliciously trying to circumvent any protective measures you put in place
- 4. One illustration of the difference Software testing determines whether a given program implements a desired functionality – Test I/O characteristics – Q/A How do you test whether a program does not allow for undesired functionality? – Penetration testing helps, but only up to a point
- 5. Security is interdisciplinary Draws on all areas of CS – Theory (especially cryptography) – Networking – Operating systems – Databases – AI/learning theory – Computer architecture/hardware – Programming languages/compilers – HCI, psychology
- 6. Fortunately, we are winning the security battle Strong cryptography Firewalls, intrusion detection, virus scanners Buffer overflow detection/prevention User education
- 8. Philosophy of this course We are not going to be able to cover everything – We are not going to be able to even mention everything Main goals – A sampling of many different aspects of security – The security “mindset” – Become familiar with basic acronyms (RSA, SSL, PGP, etc.), and “buzzwords” (phishing, …) – Become an educated security consumer – Try to keep it interesting with real-world examples and “hacking” projects You will not be a security expert after this class (after this class, you should realize why it would be dangerous to think you are) You should have a better appreciation of security issues after this class
- 10. Administrative Me TA Contact information, office hours, listed on course webpage
- 11. Course webpage http://www.cs.umd.edu/~jkatz/security/f09 Syllabus – Subject to change… – Slides will be posted for convenience, but they are not a substitute for attending lecture – Assigned readings Homeworks distributed from the course webpage Check frequently for announcements
- 12. Course blog http://cmsc414.wordpress.com I will post after each lecture – Students can post questions/comments about the lecture – Today: post a “hello” message, and answer the question: “What do you hope to get from the course?” I will post for each homework – Students can post questions I will post links to interesting news articles, papers, etc.
- 13. Textbook Recommended text: – “Network Security…” by Kaufman, Perlman, and Speciner (most recent edition) – Will only be used for a portion of the course Several other good texts out there – Ask me if you are interested Will supplement with other readings (distributed on class webpage)
- 14. Class participation and readings Research papers and news articles will be posted on the course webpage – Read these before class and come prepared to discuss Material from these readings is fair game for the exams, even if not covered in class Several readings already assigned
- 15. Course requirements Homeworks – About 4-5 throughout the semester – Programming portion will be done with a partner Each student will receive a computer account – You should have already been assigned a GRACE account
- 17. Syllabus I Introduction… – Is security achievable…? – A broad perspective on security Cryptography – The basics (take CMSC 456 or read my book for more) • If you took 456 with me, you can skip – Cryptography is not the whole solution… – …but it is an important part of the solution – Along the way, we will see why cryptography can’t solve all security problems
- 18. Syllabus II System security – General principles – Security policies – Access control – OS security – “Trusted computing” Programming language security – Buffer overflows, input validation errors – Viruses/worms
- 19. Syllabus III Network security – Identity, PKI – Authentication and key exchange protocols – Password and biometric authentication – Anonymity and pseudonymity – Privacy – Some real-world protocols (IPSec/SSL) – Attacks on network infrastructure (routing, DNS, DDos) – Wireless security
- 20. Syllabus IV Miscellaneous – Database security – Web security – Other topics (spam, …)
- 21. A High-Level Introduction to Computer Security
- 22. A naïve view Computer security is about CIA: – Confidentiality, integrity, and availability These are important, but security is about much more…
- 24. In reality… Where does security end? password forgot password?
- 25. One good attack Use public records to figure out someone’s password – Or, e.g., their SSN, so can answer security question… The problem is not (necessarily) that SSNs are public The problem is that we “overload” SSNs, and use them for more than they were intended Note: “the system” here is not just the computer, nor is it just the network…
- 26. A naïve view Achieve “absolute” security
- 27. In reality… Absolute security is easy to achieve! – How…? Absolute security is impossible to achieve! – Why…? Good security is about risk management
- 28. Security as a trade-off The goal is not (usually) “to make the system as secure as possible”… …but instead, “to make the system as secure as possible within certain constraints” (cost, usability, convenience) Must understand the existing constraints – E.g., passwords…
- 29. Cost-benefit analysis Important to evaluate what level of security is necessary/appropriate – Cost of mounting a particular attack vs. value of attack to an adversary – Cost of damages from an attack vs. cost of defending against the attack – Likelihood of a particular attack Sometimes the best security is to make sure you are not the easiest target for an attacker…
- 30. “More” security not always better “No point in putting a higher post in the ground when the enemy can go around it” Need to identify the weakest link – Security of a system is only as good as the security at its weakest point… Security is not a “magic bullet” Security is a process, not a product
- 31. Computer security is not just about security Detection, response, audit – How do you know when you are being attacked? – How quickly can you stop the attack? – Can you identify the attacker(s)? – Can you prevent the attack from recurring? Recovery – Can be much more important than prevention Economics, insurance, risk management… Offensive techniques Security is a process, not a product…
- 32. Computer security is not just about computers What is “the system”? Physical security Social engineering – Bribes for passwords – Phishing “External” means of getting information – Legal records – Trash cans Security is a process, not a product…(!)
- 33. Security mindset Learn to think with a “security mindset” in general – What is “the system”? – How could this system be attacked? • What is the weakest point of attack? – How could this system be defended? • What threats am I trying to address? • How effective will a given countermeasure be? • What is the trade-off between security, cost, and usability?
- 34. An example: airline security Ask: what is the cost (economic and otherwise) of current airline security? Ask: do existing rules (e.g., banning liquids) make sense? Ask: are the tradeoffs worth it? – (Why do we not apply the same rules to train travel?) – (Would spending money elsewhere be more effective?) Ask: how would you get on a plane if you were on the no-fly list? – (I will not give you the answer – you can find it online) – This is a thought experiment only!
- 35. Summary “The system” is not just a computer or a network Prevention is not the only goal – Cost-benefit analysis – Detection, response, recovery Nevertheless…in this course, we will focus on computer security, and primarily on prevention – If you want to be a security expert, you need to keep the rest in mind
- 36. Why is computer security so hard? Computer networks are “systems of systems” – Your system may be secure, but then the surrounding environment changes Too many things dependent on a small number of systems Society is unwilling to trade off features for security Ease of attacks – Cheap – Distributed, automated – Anonymous – Insider threats Security not built in from the beginning Humans in the loop… Computers ubiquitous…
- 37. Computers are everywhere… …and can always be attacked Electronic banking, social networks, e-voting iPods, iPhones, PDAs, RFID transponders Automobiles Appliances, TVs (Implantable) medical devices Cameras, picture frames(!) – See http://www.securityfocus.com/news/11499
- 38. “Trusting trust” (or: how hard is security?)
- 39. “Trusting trust” Consider a compiler that embeds a trapdoor into anything it compiles How to catch? – Read source code? (What if replaced?) – Re-compile compiler? What if the compiler embeds the trojan code whenever it compiles a compiler? – (That’s nasty…)
- 40. “Trusting trust” Whom do you trust? Does one really need to be this paranoid?? – Probably not – Sometimes, yes Shows that security is complex…and essentially impossible Comes back to risk/benefit trade-off