USC CSCI430 Security Systems Lecture notes – Spring 2015 Dr. Jelena Mirkovic University of Southern California Information Sciences Institute

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Contact Instructor – Dr. Jelena Mirkovic – Office hours W or by appt in PHE 514/516 – Contact via (on class web page)

Grading Grading: – CTF exercises: 20% – Homeworks: 20% – Participation: 10% – Midterm Exam: 20% – Final Exam: 30% Grades assigned using an absolute curve: AA-B+BB-C+CC-D+DD

Homeworks Done on DeterLab testbed – I will open an account for each of you after the class – You will get an automated how to log on – Your assignment for the next class – readings linked on the Web page AND run a sample experiment to learn how to use DeterLab. It could be the one from tutorial. We’ll have 4 homeworks, each carries 5% of your grade Ask for help early Do NOT testbed ops when you have a problem: – myself or TA – We can either help with an issue, find out help from DeterLab staff or extend a deadline – We will take points off if you testbed-ops!

Class 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 – Schedule is paramount! You have to develop code early and test it thoroughly: This cannot be done a day before the exercise I will set some milestones for you to ensure timely progress

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 (Piazza) – I will check the discussion boards once daily but if you want a reliable response from me me directly Class participation carries 10% of your grade

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 or TA 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? (this list is not exhaustive) 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 exploited makes it behave in a way that system’s creator did not expect. An exploit is a set of steps that exercises the vulnerability

Attacking my computer o Denial-of-service attacks o Viruses and some worms A virus is a self-replicating program that requires user action to activate such as clicking on , downloading an infected file or inserting an infected floppy, CD, etc.. A worm is a self-replicating program that does not require user action to activate. It propagates itself over the network, infects any vulnerable machine it finds and then spreads from it further. A DOS attack aims to disrupt a service by either exploiting a vulnerability or by sending a lot of bogus messages to a computer offering a service What Are the Threats? (this list is not exhaustive)

Stealing my information o From my computer or from communication o 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? (this list is not exhaustive)

Using my machine to attack others o viruses o Worms o Denial-of-service attacks (including reflector attacks) o Spam, phishing What Are the Threats? (this list is not exhaustive)

Damaging my computer or data o I have to prevent break-ins o I will also use cryptography to detect tampering o I must replicate data to recover from tampering o Denial-of-service attacks and worms can sometimes damage computers What Are the Threats? (this list is not exhaustive)

Taking up my resources with irrelevant messages o Denial-of-service attacks o Spam mail (takes time to read and fills space) o Viruses and worms What Are the Threats? (this list is not exhaustive)

Messing up with my physical world o Cyber-physical attacks or collateral victims o Power systems, traffic control, utilities o Travel agencies o Medical devices o Smart vehicles What Are the Threats? (this list is not exhaustive)

Pretending to be Alice or myself or our computers o 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 the sender field of IP packets. What Are the Threats? (this list is not exhaustive)

Preventing me from communicating with Alice o Alice could be attacked o Routers could be overloaded or tampered with o DNS servers could be attacked What Are the Threats? (this list is not exhaustive)

Some Security Mechanisms (this list is not exhaustive) 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 field o No problem is likely to be completely solved o New advances lead to improvement of attack techniques o 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 attack traffic o 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