USC CSci499Security Systems Lecture notes – Spring 2013

Dr. Jelena MirkovicUniversity of Southern CaliforniaInformation Sciences Institute

Class home page

• http://ccss.usc.edu/499 – Syllabus– Assignments– News– Lecture notes

• Keep checking it!

Contact

• Instructor– Dr. Jelena Mirkovic– Office hours Fri 1-2pm or by appt in SAL 214/216– Contact via email (on class web page)

Grading• Grading:– CTF exercises: 20%– Homeworks: 20%– Quizzes: 5%– Participation: 5%– Midterm Exam: 20%– Final Exam: 30%

• Grades assigned using an absolute curve:A A- B+ B B- C+ C C- D+ D D

90 86 83 80 76 73 70 66 63 60 56

Homeworks• Done on DeterLab testbed– I will open an account for each of you after the class– You will get an automated email how to log on– Your assignment for the next class – read through the

tutorial (at http://www.deterlab.net) and run a sample experiment to learn how to use DeterLab

• We’ll have 4 homeworks, each carries 5% of your grade• Ask for help early• Do NOT email testbed ops, I can help with all DeterLab

issues

Capture-the-Flag Exercises• Done on DeterLab testbed• Blue team develops some technology, Red team

attacks it• Everyone will have a chance to be on both teams• Each exercise will be performed in class, each carries

10% of your grade– I’m not looking for extraordinary solutions (although they

are welcome) but for good integration of what you learned in class and what you managed to learn off the Internet

– Teamwork is important

Quizzes• Done before each homework exercise• Repeated after the exercise• You MUST take each quiz• Total 5% of your grade

Midterm and Final• Closed book, closed notes• Each last 1 h 20 min• We will have reviews in class before each

Class Participation• Class participation is important– Ask and answer questions in class– Ask, answer, participate on-line

• Class participation carries 5% of your grade

DEN• DEN system will host the class discussion board– To gain access and log in

https://mapp.usc.edu/– Contact webclass@usc.edu if you have difficulty with

the system– I will check the discussion board once daily but if you

want a reliable response from me email me directly

Academic Integrity• What is and is not OK– I encourage you to work with others to learn the material

but everyone must DO their work ALONE– Do not to turn in the work of others– Do not give others your work to use as their own– Do not plagiarize from others (published or not)– Do not try to deceive the instructor

• See the Web site– More guidelines on academic integrity– Links to university resources– Ask if in doubt

• You can always ask me for help!

What Does Security Mean?

What Does Security Mean?… In Real Life

• No one should be able to: – Break into my house– Attack me– Steal my TV– Use my house to throw water balloons on people– Damage my furniture– Pretend to be my friend Bob and fool me – Waste my time with irrelevant things– Prevent me from going to my favorite restaurant– Destroy my road, bridge, city ..

What Does Security Mean?… wrt Computers and Nets

• No one should be able to:– Break into my computer– Attack my computer– Steal my information – Use my computer to attack others– Damage my computer or data– Use my resources without my permission– Mess with my physical world

• I want to talk to Alice– Pretend to be Alice or myself or our computers– Prevent me from communicating with Alice

Computer vs. Network Security• An isolated computer has a security risk?

– Computer security aims to protect a single, connected, machine

• Networking = communication at all times and in all scenarios!!!– Network security aims to protect the communication

and all its participants

• Security = robustness or fault tolerance?

Computer security Network security

Security Properties• Confidentiality (C)– Keep data secret from non-participants

• Integrity (I)– Aka “authenticity”– Keep data from being modified– Keep it functioning properly

• Availability (A)– Keep the system running and reachable

Orthogonal Aspects

• Policy– Deciding what confidentiality, integrity and availability

mean• Mechanism– Implementing the policy

Security Goals

• Attack prevention– It is impossible for the attack to succeed

• Attack detection– Low false positives, false negatives and detection delay

• Attack response– Retaliation, observation, recovery

• Attack recovery– Remedy the effects of the attack or sustain it

A false positive is when the system detects an attack, but the attack did not occur. A false negative is when the attack is missed by the system.

What Does Security Mean?… wrt Computers and Nets

• No one should be able to:– Break into my computer – A, C, I– Attack my computer – A, C, I– Steal my information - C– Use my computer to attack others – I?– Damage my computer or data - I– Use my resources without my permission – A– Mess with my physical world – I, A

• I want to talk to Alice– Pretend to be Alice or myself or our computers – C, I– Prevent me from communicating with Alice - A

What Are the Threats?• Breaking into my computer

o Hackers• Break a password or sniff it off the network• Exploit a vulnerability

• Use social engineering• Impersonate someone I trust

o Viruses and worms

A vulnerability is a weakness in the system (its design, implementation or use procedures) that when exploitedmakes it behave in a way that system’s creator did not expect. An exploit is a set of steps that exercises the vulnerability

What Are the Threats?• Attacking my computer

o Denial-of-service attacks

o Viruses and some worms

A virus is a self-replicating program that requiresuser action to activate such as clicking on E-mail,downloading an infected file or inserting an infectedfloppy, CD, etc ..A worm is a self-replicating program that does notrequire user action to activate. It propagates itselfover the network, infects any vulnerable machine itfinds and then spreads from it further.

A DOS attack aims to disrupt a service by either exploiting a vulnerability or by sending a lot ofbogus messages to a computer offering a service

What Are the Threats?

• Stealing my information o From my computer or from communicationo I will use cryptography!

• There are many ways to break ciphers• There are many ways to divulge partial information

(e.g. who do you talk to)o I would also like to hide who I talk to and when

• I will use anonymization techniques• Anonymization hinders other security approaches

that build models of normal traffic patterns

What Are the Threats?

• Using my machine to attack otherso E-mail viruseso Wormso Denial-of-service attacks (including reflector attacks)o Spam, phishing

What Are the Threats?

• Damaging my computer or datao I have to prevent break-inso I will also use cryptography to detect tamperingo I must replicate data to recover from tamperingo Denial-of-service attacks and worms can sometimes

damage computers

What Are the Threats?

• Taking up my resources with irrelevant messageso Denial-of-service attackso Spam mail (takes time to read and fills space)o Viruses and worms

What Are the Threats?

• Messing up with my physical worldo Cyber-physical attacks or collateral victims

o Power systems, traffic control, utilitieso Travel agencieso Medical deviceso Smart vehicles

What Are the Threats?

• Pretending to be Alice or myself or our computerso I want to be sure who I am talking to

(authentication and digital signatures)o It is hard to impersonate a computer in two-way

communication, such as TCP• But it has been done

o Plain IP spoofing seems an extremely hard problem to solve

IP spoofing means putting a fake IP address in thesender field of IP packets.

What Are the Threats?• Preventing me from communicating with Alice

o Alice could be attackedo Routers could be overloaded or tampered witho DNS servers could be attacked

Some Security Mechanisms• Encryption• Checksums• Key management• Authentication• Authorization• Accounting• Firewalls

• VPNs• Intrusion Detection• Intrusion Response• Virus scanners• Policy managers• Trusted hw

What Are the Challenges?• Your security frequently depends on others– Tragedy of the Commons

• A good solution must – Handle the problem to a great extent– Handle future variations of the problem, too– Be inexpensive– Have economic incentive– Require a few deployment points– Require non-specific deployment points

What Are the Challenges?• Fighting a live enemy

o Security is an adversarial fieldo No problem is likely to be completely solved o New advances lead to improvement of attack

techniqueso Researchers must play a double role

What Are the Challenges?• Attack patterns change• Often there is scarce attack data• Testing security systems requires reproducing or

simulating legitimate and traffico No agreement about realistic traffic patterns

• No agreement about metrics• There is no standardized evaluation procedure• Some security problems require a lot of resources

to be reproduced realistically

Practical Considerations

• Risk analysis and risk management– How important it is to enforce a policy– Which threats matter– Legislation may play a role

• The role of trust– Assumptions are necessary

• Human factors– The weakest link

In The Shoes of an Attacker

• Who are the attackers– Used to be teenage hackers (bragging rights)– Now organized criminal (for profit)– Political organizations

• Risk to the attacker– Usually very small