CS 261, Fall 2007
Computer Security

  David Wagner (daw@cs, 629 Soda Hall, 642-2758)

  Tu-Th, 5:00-6:30, 310 Soda

Office Hours:
  Wagner: Tu 1-2pm in 629 Soda.


Course Description

CS261: Security in Computer Systems. Prerequisite: CS162. Graduate survey of modern topics in computer security, including: protection, access control, distributed access control, Unix security, applied cryptography, network security, firewalls, secure coding practices, safe languages, mobile code, and case studies from real-world systems. May also cover cryptographic protocols, privacy and anonymity, and/or other topics as time permits. Term paper or project required. Three hours of lecture per week. (3 units)

Prerequisites: CS 162 or equivalent. Familiarity with basic concepts in operating systems and networking.

Course topics

An approximate list of course topics (subject to change; as time permits):

Basic concepts
Trust, trusted computing base, trusted path, transitive trust. Reference monitors. Policy vs. mechanism. Assurance. Lessons from the Orange Book.
Access control
Authorization, policy, access matrix. Subjects and objects. ACLs, capabilities. Rings, lattices. Revocation. Groups. The role of crypto. Distributed access control. Mandatory vs. discretionary access control, compartmentalization, covert channels.
Traditional OS centralized protection: address spaces, uids, resource management. The Unix security model: file permissions, the super-user, setuid programs, system calls, password security. How networks change the problem space.
Secure coding
Design principles: code structure, least privilege, small security kernels, small interfaces. Tools: language support, type-safe languages, static checking. Common vulnerabilities: buffer overruns, setuid programs, the confused deputy, race conditions, improper canonicalization.
Symmetric key, public key, certificates. Choosing an algorithm. Protocols. Integrity, authenticity confidentiality, availability. Non-repudiation.
Network security
TCP/IP. Attacks on network protocols: address spoofing, hijacking, source routing, SYN floods, smurfing, etc. DNS attacks, routing vulnerabilities. Attacks on network daemons. The Internet Worm. TCP wrappers. Intrusion detection .
Philosophy, benefits. Styles: packet filter, application proxying, stateful inspection. Performance, scalability. Fail-safety, assurance. Techniques. Do's and don'ts.
Confining untrusted code
Motivation: the mobile code problem, implementing least privilege. Mechanisms: signed code, interpreted code, software fault isolation, proof-carrying code, virtualization, extensible reference monitors. Practical experience: ActiveX, Java, Javascript.
Case studies
Kerberos. PGP and the web of trust. SSL and centralized certification authorities. SSH. IPSEC. Cellphones. Therac-25. Practical issues: risk management, key management, smartcards, copy protection systems, social engineering.
Extra topics
Privacy: Anonymity and traffic analysis; remailers and rewebbers; practical experience. Cryptographic protocols: protocol failures, design principles; logics of authentication; Formal methods. Others as time permits and according to student interest.


Class project: 40%
Problem sets: 40%
Scribe notes: 10%
Paper summaries and class discussion: 10%


There will be a term project. You will do independent research in small groups (e.g., teams of 2--3). Projects may cover any topic of interest in systems security, interpreted broadly (it need not be a topic discussed in class); ties with current research are encouraged. A conference-style report on your results will be due (date to be determined).

Information on projects is now available. The project proposal is due October 15th. The poster session will be held Dec 5th, 4-6pm, in the Woz lounge. The final reports will be due Monday, Dec 17th, at 9am.

The list of project groups is available.

You are encouraged to start thinking of topics of interest early. Be ambitious! I expect that the best papers will probably lead to publication (with some extra work).

Problem Sets

There will be approximately two to four homework assignments throughout the semester, to appear on the course webpage as they are assigned.

Turn in your homeworks on paper at the beginning of class on the day they are due. Due dates will be enforced strictly. Late homeworks will not be accepted.

Work on your own when doing homeworks. You may use any source you like (including other papers or textbooks), but if you use any source not discussed in class, you must cite it.

Scribe notes

You will be expected to write scribe notes for one lecture. Email me an PDF file with your scribe notes within one week after the lecture you are assigned to scribe.


There is no required textbook. All reading will be from papers. Whenever possible, handouts and papers will be placed online on the web page; papers not available online will be handed out in class. A schedule of assigned readings is available below.

You will be required to write a brief summary of each paper you read. Submit your summary, on paper, before the beginning of the class when the reading is due. Your summary should list: (i) the two or three most significant new insights you took away from the paper, and (ii) its two or three most significant flaws or weaknesses or how the paper could be improved. Your summary does not need to be formal (you may use bullet lists, incomplete sentences, etc.), and it may be brief, but you should give it some thought.


From time to time, we may discuss vulnerabilities in widely-deployed computer systems. This is not intended as an invitation to go exploit those vulnerabilities. It is important that we be able to discuss real-world experience candidly; students are expected to behave responsibly.

Berkeley's policy (and my policy) on this should be clear: you may not break into machines that are not your own; you may not attempt to attack or subvert system security. Breaking into other people's systems is inappropriate, and the existence of a security hole is no excuse.


The following schedule is highly tentative and subject to change.

Topic Readings Notes
8/28 Overview; intro; threat models (none) [handout] Igor Ganichev, Peter Lau
8/30 Principles of secure design (none) [slides]
9/4 Access control, protection (none) Colleen Lewis, Steve Hanna
9/6 Software vulnerabilities Beyond Stack Smashing: Recent Advances in Exploiting Buffer Overruns, Pincus, Baker.
Exploiting Format String Vulnerabilities.
Basic Integer Overflows.
DK Moon
9/11 Runtime defenses A Practical Dynamic Buffer Overflow Detector, Ruwase, Lam.
Taint-Enhanced Policy Enforcement: A Practical Approach to Defeat a Wide Range of Attacks, Xu, Bhatkar, Sekar.
Ashima Atul
9/13 Static analysis MECA: an Extensible, Expressive System and Language for Statically Checking Security Properties, Yang, Kremenek, Xie, Engler.
Finding Security Vulnerabilities in Java Applications Using Static Analysis, Livshits, Lam.
Man-Kit Leung
9/18 Inline reference monitors Evaluating SFI for a CISC Architecture, McCamant, Morrisett. Udam Saini
9/20 Sandboxing A secure environment for untrusted helper applications: confining the wily hacker, Goldberg, Wagner, Thomas, Brewer. Barret Rhoden
9/25 Sandboxing Traps and Pitfalls: Practical Problems in System Call Interposition Based Security Tools, Garfinkel.
Yu (David) Zhu
9/27 Privilege separation Preventing Privilege Escalation, Provos, Friedl, Honeyman.
Shifting the odds: Writing (more) secure software, Bellovin.
10/2 Privilege management Extensible security architectures for Java, Wallach, Balfanz, Dean, Felten. Shoaib Kamil
10/4 Capabilities The Confused Deputy, Hardy.
The Oz-E Project: Design Guidelines for A Secure Multiparadigm Programming Language, Spiessens, Van Roy (skip Section 5).
Cynthia Sturton
10/9 Network security A look back at Security Problems in the TCP/IP Protocol Suite, Bellovin. Yanpei Chen
10/11 (No class)
10/16 Firewalls Firewall Gateways, Chapter 3 of Firewalls and Internet Security: Repelling the Wily Hacker, Cheswick and Bellovin (1st ed). Steve Houston
10/18 Application-level firewalls (no readings)
10/23 DNS security Using the Domain Name System for System Break-Ins, Bellovin. Karen Hsu
10/25 Intrusion detection Bro: A System for Detecting Network Intruders in Real-Time, Paxson. Bor-Yiing (Brian) Su
10/30 Attacks Inside the Slammer Worm, Moore, Paxson, Savage, Shannon, Staniford, Weaver.
A Multifaceted Approach to Understanding the Botnet Phenomenon, Rajab, Zarfoss, Monrose, Terzis.
Erika Chin
11/1 Usable security Why Johnny Can't Encrypt, Whitten, Tygar Florent Robineau
11/6 Web security The Emperor's New Security Indicators: An evaluation of website authentication and the effect of role playing on usability studies, Schechter, Dhamija, Ozment, Fischer
Security for GWT Applications, Google
11/8 Mobile code, Cryptography (none)
11/13 Cryptography Why Cryptosystems Fail, Anderson. Gunho Lee
11/15 Kerberos Designing an Authentication System: a Dialogue in Four Scenes, Bryant. John Bethencourt
11/20 Cryptographic protocols Prudent engineering practice for cryptographic protocols, Abadi, Needham. Thomas Kho; slides
11/22 No class! (Thanksgiving holiday)
11/27 E-voting Security Analysis of the Diebold AccuVote-TS Voting Machine, Feldman, Halderman, Felten Armando Solar-Lezama
11/29 Privacy Privacy, economics, and price discrimination on the internet, Odlyzko Vahab Pournaghshband
12/4 Untrusted platforms How to Hurt the Hackers: The Scoop on Internet Cheating and How You Can Combat It, Pritchard
12/6 Economics, wrap-up Why Information Security is Hard - An Economic Perspective, Anderson


I always welcome any feedback on what I could be doing better. If you would like to send anonymous comments or criticisms, please feel free to use an anonymous remailer to send me email without revealing your identity, like this one or this one.

David Wagner, daw@cs.berkeley.edu, http://www.cs.berkeley.edu/~daw/.