CMPS 122: Computer Security

Transcription

1 CMPS 122: Computer Security Introduction Today s goals Course introduction Course overview Course logistics (details on the syllabus) Introduction to computer security What is computer security? Goals Attacks Who? How? Defenses Introduction 2 1

2 Welcome! Ethan Miller Office: 265 E2 Hours: Tue 11:00 noon Thu 12:30 1:30 PM Alisa Neeman Office: Hours: Mon 10:00 11:00 AM Wed 2:00 3:00 PM No discussion section or lab hours Ask us questions during office hours Class web page (assignments, slides, announcements, etc.) Introduction 3 Class outline Introduction & concepts Encryption & authentication Secure network protocols (Kerberos, SSL) Program security Bug exploits Malcode: viruses, worms, trojan horses, and more Writing safe code Attacks and defenses on computer systems Firewalls Intrusion detection Countermeasures Trusted operating systems Introduction 4 2

3 Textbooks Required Cryptography and Network Security (Stallings) Recommended Secrets and Lies (Schneier) Firewalls and Internet Security, 2nd Edition (Cheswick, Bellovin, Rubin) Introduction 5 Course requirements Two exams Midterm in the 5th 6th week Final exam Homework 5 6 homeworks during the quarter About one week per homework Graded Need not do every homework to pass the class Missing homeworks count as a zero! Hand in online Term project More on this in a bit Introduction 6 3

4 How are grades determined? Final grades based on: Homework: 30% all homeworks weighted equally Midterm: 16% Final: 24% Final project: 25% Class participation: 5% Approximate grade ranges: A: 89% 100% B: 79% 88% C: 69% 78% D: 60% 68% To pass the class, you must Take both exams Turn in a final project Have at least a 50% average on exams and 50% average on homework Satisfying both conditions does not guarantee a passing grade Introduction 7 Other ways to change your grade Up Solve a challenge problem (not normal homework) Find a security hole and have it published by a national organization (CERT, Mercury News, Time magazine ) Down Send me a virus ( or otherwise) Doesn t count if the virus is neutralized and sent as an FYI viruses that attack your address book do count Get arrested for a computer security attack Get convicted for a computer security attack To an F/U/NP (i.e., fail!) Get me arrested for something you do related to this class Cheat (we will catch you) Introduction 8 4

5 Homework Homework lets you Try to solve (or create) computer security problems Test your knowledge and understanding of the subject Homework isn t optional! Homework must be your own work! Programming may be required Use any language you want Use any sources you like, if you cite them Keep in mind that I ll take a dim view of copying someone else in class If the assignment requires that you write your own code, you may not get full credit for using someone else s code In many cases, the biggest benefit is the process! Introduction 9 Challenge problems Open until solved or last day of class First satisfactory answer gets bonus Later answer might still get bonus if it s better Solving in groups is OK Each member gets n/n * value (e.g., 3 people = 3/3 = 0.58) Unlike homework, there s not necessarily a correct answer (or even a solution!) Challenge problems will be listed on the course Web page Introduction 10 5

6 Final project Write a paper on a topic related to computer security Review several research papers Analyze the security of a particular system Compare the security or performance of several cryptosystems Evaluate security products (firewalls, software, etc.) Explore ways to write more secure code Lots of other possibilities Suggested topics will be posted on the class web site Papers should be about 7 8 pages long Introduction 11 Getting help Computer security can be a tough subject get help if you need it! I m here to help you learn the material It s up to you to ask for help Don t wait too long! Ask questions in class Visit office hours Ask general questions on the course newsgroup Ask specific questions by Expect short answers, not long explanations Introduction 12 6

7 What is cheating? Cheating is: Copying answers from your fellow students Having someone else do your project for you Using material without attribution Cheating is not: Studying in a group: your fellow students are a great resource for understanding difficult material Discussing homework in general terms Using information from the Web, assuming you write down where you got it Copying answers off the Web may be cheating, though. Everything you turn in should be yours Document completely if it s not! Use common sense: if you re not sure, ask me before doing it Introduction 13 The Simpsons rule You may discuss homework with others General issues only You may not take notes You must take a 30 minute break before working on any CMPS 122 assignments Watch the Simpsons or good Warner Brothers cartoons Watch mindless TV Work on other classes Take a nap Introduction 14 7

8 Why should you take this course? Reason #1: Fate of Humanity Cryptography plays a central role in human history Survival of humanity depends on computer security Reason #2: Intellectual Curiosity Cryptology and computer security are about making and solving puzzles It s fun to do this! Reason #3: $$$ Computer security is a growing business There are always jobs for people who know how to keep vital computer resources safe Introduction 15 Bad reasons for taking this class You want to write the ultimate virus to wipe the world s hard drives clean You want to show (by doing) just how insecure Windows is You want to break into (UCSC s the NSA s your bank s) computer systems You re bored, and there s nothing better to take this quarter (I guess this isn t so bad) Introduction 16 8

9 What is security? Keeping something (information in our case) secure against Someone stealing it Someone destroying it Someone changing it Someone preventing me from using it More specifically Confidentiality: nobody else can see it Integrity: nobody else can change it Availability: I can get at it whenever I want Introduction 17 Security on physical things Use physical security rather than computer security Access to valuables was more difficult to obtain Had to be physically present in many cases! Moving the valuable could be difficult Alteration was easier to notice Physical marks were left if you tried to change something Physical goods had one copy If you have the copy, I don t No notion of multiple parties sharing the item Physical security could be Expensive: need to hire guards Difficult & dangerous: people got injured or killed Introduction 18 9

10 Security on information: the old way Information isn t like a physical object Copies can be made inexpensively A copy doesn t prevent the original from being used Easy to transport Less need for physical presence Value can be very high for small data Before computers, some things were still easy Integrity easier to check: look for signs of alteration Confidentiality: keep it a locked bank vault (and hope there are no bank robbers) Availability: only when the bank is open Introduction 19 Security in computing More difficult because of the nature of computers Confidentiality Easier to break into a networked computer without physical presence Easy to spread information around the world in minutes Integrity No signs that information has been altered Can t easily check to see if someone might have had access to the information to alter it Availability All the old ways of denying access still work Physical attacks Destroying the information New ways exist Keep the computer too busy to respond Prevent authorized users from seeing the information Introduction 20 10

11 Addressing security issues What are the risks? How likely is each one? How expensive would it be if the risk came to pass? What are the available countermeasures? How expensive are they to implement? How inconvenient are they? What are the vulnerabilities? Simple design flaws more than basic problems How can they be addressed? Bug fixes Workarounds Introduction 21 Computer intrusions This is (usually) a crime! Typically done for one of two reasons Commercial gain Fun Commercial gain Go after the most valuable item: often information Information can be Destroyed: loss of use to the owner Copied: used by a competitor for commercial advantage Fun Because it s there Because I disagree with their policies In both cases, intrusions follow the path of least resistance Strong security in one area doesn t cover for weak security elsewhere Relative security of different mechanisms can change over time Introduction 22 11

12 Attacks: terminology Attacks can be made on any of Hardware Software Data (information) Terms Threat: circumstances that may lead to loss or harm Vulnerability: weakness in the security system Control: something that reduces or removes a vulnerability Types of attacks Interception: unauthorized party gets access to an asset Interruption: asset becomes unusable (lost or destroyed) Modification: existing asset is changed Fabrication: fake asset is planted in the system Introduction 23 Goals of computer security Ensure that the system maintains Confidentiality Integrity May have many different (conflicting) meanings Must specify what it means in this case Availability Responds at all? Responds in a timely fashion? Can be used as it was intended? Has sufficient capacity? Others Maintaining these properties can be difficult! Introduction 24 12

13 Vulnerabilities Interruption Interception Modification Fabrication Hardware Denial of service Physical attack Theft Planting fake computers Software Data Deletion Deletion Unauthorized copying Surveillance Insider theft Logic bomb Trojan horse Virus Trapdoor Information leak Modify databases Change files Fake (or modified) software False records Introduction 25 Types of intruders Amateurs People who steal resources for their own uses Typically unsophisticated Crackers Access resources without permission Typically for fun, but may be other reasons Career criminals Well-planned attacks Usually for financial gain Military Done to disable opposing forces, typically Gain strategic advantage Introduction 26 13