Tuomas AuraT-110.4206 Information security technology

Lecture 1:Computer security overview

Aalto University, autumn 2011

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Outline

Timeline of computer security What is security anyway? Summary

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TIMELINE OF COMPUTER SECURITY

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70s Multi-user operating systems need for protection

Access control models: multi-level security, Bell-LaPadula 1976, BIBA 1977

DES encryption algorithm 1976 cryptanalysis, need for key distribution

Public-key cryptosystems:Diffie-Hellman 1976, RSA 1978

Key distribution: certificates 1978 key exchange protocols: Needham-Schroeder 1978

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80s Orange Book 1985: mandatory access control Accounting Commercial security models from accounting

and auditing rules: Clark-Wilson 1987 X.509 PKI 1988 IBM PC software copy protection floppy virus 1987

Internet Morris worm 1988

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90s Methodological approach to security research:

Information flow security Secure operating systems: SEVMS –1996 Formal analysis of key exchange protocols

Wider availability of cryptography – Cellular networks: GSM 1991– Open-source cryptography: PGP 1991– Password sniffers SSH 1995– Commercial Internet SSL ja VeriSign CA 1995– RSA patent expired in 2000

Spam: Cantor and Siegel 1994 PKI criticism trust management User authentication beyond passwords Intrusion detection Macro virus: Melissa 1999 DRM

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2000s Fast-spreading Internet worms: Code Red 2001 secure programming secure programming languages security analysis and testing tools

Botnets, spyware malware analysis Computer crime: phishing Enterprise identity management Security in mobility, Grid, ah-hoc networks, sensor

networks Social networks Privacy concerns

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WHAT IS SECURITY

What is security When talking about security, we are concerned

about bad events caused with malicious intent – Security vs. reliability

Terminology:– Threat = bad event that might happen– Attack = someone intentionally causes the bad thing

to happen– Vulnerability = weakness in an information system

that enables an attack– Exploit = implementation of an attack– Risk = probability of an attack × damage in dollars

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Security Goals CIA = confidentiality, integrity, availability– Confidentiality — protection of secrets – Integrity — only authorized modification of data and

system configuration– Availability — no denial of service, business

continuity Examples: secret agent names, web server The CIA model is a good starting point but not all:– Access control — no unauthorized use of resources– Privacy — control of personal data and space– What else?

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Areas of IT security[Gollmann] Computer security — security of end hosts and

client/server systems– Focus: access control in operating systems– Example: access control lists for file systems

Network security — security of communication– Focus: protecting data on the wire– Example: encryption to prevent sniffing

Application security — security of services to end users and businesses– Focus: application-specific trust relations– Example: secure and legally binding bank transactions

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Viewpoints to security Cryptography (mathematics) Computer security (systems research) Network security (computer networking) Software security (software engineering, programming

languages and tools) Formal methods for security (theoretical CS) Hardware security (HW engineering) Human aspects of security (usability, sociology) Security management (information-systems management,

enterprise security) Economics of security, laws and regulationYou cannot be just a security expert! Need broaderunderstanding of the systems and applications

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Security is a continuous process Continuous race between attackers and defenders

– Attackers are creative No security mechanisms will stop all attacks; attackers just

move to new paths and targets– Some types of attacks can be eliminated but others will take

their place– Compare with crime statistics: Do locks or prison reduce crime

in the long term? Security mechanisms will fail and new threats will arise

→ Monitoring and auditing for new attacks→ Contingency planning: how to recover from a breach

Network security is more straightforward than application security, but difficult enough

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Cost vs. benefit Rational attackers compare the cost of an attack with the

gains from it– Attackers look for the weakest link; thus, little is gained by

strengthening the already strong bits Rational defenders compare the risk of an attack with the

cost of implementing defenses– Lampson: “Perfect security is the enemy of good security”

But human behavior is not always rational:– Attackers follow each other and flock all to the same path– Defenders buy a peace of mind; avoid personal liability by

doing what everyone else does→ Many events are explained better by group behavior than

rational choice

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Proactive vs. reactive security Technical prevention: design systems to

prevent, discourage and mitigate attacks– If attack cannot be prevented, increase its cost and

control damage Detection and reaction: detect attacks and take

measures to stop them, or to punish the guilty In open networks, attacks happen all the time– We can detect port scans, spam, phishing etc., yet

can do little to stop it or to punish attackers → Technical prevention and mitigation must be the primary defence

However, detection is needed to monitor the effectiveness of the technical prevention

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Who is the attacker? We partition the world into good and bad entities

– Honest parties vs. attackers– Good ones follow specification, bad ones do not– Different partitions lead to different perspectives on the security of

the same system Typical attackers:

– Curious or dishonest individuals — for personal gain– Hackers, crackers, script kiddies — for challenge and reputation– Companies — for economic intelligence and marketing– Security agencies — NSA, FAPSI, GCHQ, DGSE, etc.– Military SIGINT — strategic and tactical intelligence, cyber war– Organized criminals — for money

Often, not all types of attackers matter– E.g. who would you not want to read your diary?

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Security research Security research often focuses on attacks Engineers should focus on solutions BUT need

to understand– how systems fail– how the attacker thinks– adversarial mindset

Security researchers spend most of their time looking for flaws in the work of others not always welcomed by others; so be careful in how you express yourself

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Ethical considerations Who is allowed to attack and when?– Violations of policy– Causing damage

Are security policies for us or against us?– University policy vs. active learning– Difference between research or QA and crime?– Privacy of human subjects– Getting work done vs. following rules

Ethics and software engineering:– Security can be a tool for bad, as well as good

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SUMMARY

Goals of information security Security goals: confidentiality and integrity of

information, availability of services Authentication, access control, accounting Protection of services and infrastructure

in a hostile environment (e.g. Internet) Control, monitoring or privacy Business continuity

Reading material Dieter Gollmann: Computer Security, 2nd ed.,

chapters 1–2 Matt Bishop: Introduction to computer

security, chapter 1 (http://nob.cs.ucdavis.edu/book/book-intro/intro01.pdf)

Edward Amoroso: Fundamentals of Computer Security Technology, chapter 1

Ross Anderson: Security Engineering, 2nd ed., chapter 1 (1st ed. http://www.cl.cam.ac.uk/~rja14/Papers/SE-01.pdf)

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Exercises What security threats and goals are there in the postal (paper mail)

system?– What different entities are there in the postal system?– Do they have the same of different security concerns?– Who could be the attacker? Does the answer change if you think from a

different entity’s viewpoint?– Can you think of attacks where it is necessary for two or more malicious

parties to collude? What is role of laws and punishment in computer security? Can the development of information security technology be

unethical, or is engineering always value neutral? Give examples. When is it (or when could it be) ok for you to attack against IT

systems? Give examples. How do the viewpoints of security practitioners (e.g. system admin

or company security officer) and academic researchers differ?23