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