Introduction to Computer Security - Course Introduction€¦ ·  · 2011-04-20Introduction to...

Introduction to Computer SecurityCourse Introduction

Pavel LaskovWilhelm Schickard Institute for Computer Science

Computer security in headlines

Computer security in numbers

New malicious code samples observed (Symantec)

Technische Universität Berlin

Gefährliches Internet

» Internet als Risikofaktor?

» Omnipräsenz von Angriffen, Würmern und Viren» Massive Schäden bei Unternehmen und Bürgern» Zunehmende Kriminalisierung von Schadsoftware

0

750.000

1.500.000

2.250.000

3.000.000

2002 2003 2004 2005 2006 2007 2008 2009

Neuer Schadcode pro Jahr (Symantec)

What lurks behind the statistics?

Malware previously used for fun is now used for profit.78% of end user attacks involved stealing of login data76% of phishing attacks targeted financial sectorAverage cost of data breach in 2008 in the USA: 6.7M $.

Hacking is no longer the realm of “script-kiddies”.60% of malicious code threats represent new attacks.

The biggest risk resides not in but in front of a computer.Why would anyone want something from me?What does my Windows want to update again?I have already bought an antivirus, so I am safe.

Why are computer systems insecure?

Growing complexity of computer systemslarge number of components, complex interaction

High competitionshort “time-to-market”, high ROI

Leveraging of risks through high connectivityworm outbreaks, botnets

Slow incident response“incident hiding”, manual handling

Human error

What can go wrong will go wrong!

Human error: a case study

Human error: a case study

Human error: a case study

Human error: a case study

Human error: a case study

Human error: a case study

Human error: lessons learned

Users make errorselaborate social engineering designtime pressure

Significant monetary motivationBusiness efficiency via Internet

Acrobat Reader exploit

Acrobat Reader JBIG2 exploit: a timeline

Exploit discovered: ???First public warnings: 19.-20.02Adobe Reader 9.0 patched: 10.03Adobe Reader 8.1.3 patched: 18.03Adobe Reader Linux patched: 26.03Recognition by antivirus system as of mid-April 2009: 6/39(15.39%)

Infection without a click

Select a thumbnail view.Hover a mouse over a document.Do nothing: the Windows Desktop Search (if notde-activated) will find it and open!

Potential consequences of an infection

Start a keyloggerStart a botnet (zombie) clientDownload further code from a remote site

Security instruments

Security instruments

Prevention

Security instruments

Prevention

Detection

Security instruments

Prevention

Detection

Reaction

What will you learn?

Findamental concepts of computer securitydry, but important!

Basic security goals and mechanismsauthentication, access control, encryption, etc.

Practical security instrumentsWindows and Linux security.

Further selected topicsnetwork securitysoftware securityweb application and browser security

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Coarse administration

Lectures:Wed, 10:00–12:00 (ct), A301

Formalities:Credit hours (diploma): 2 SWS (lectures) + 1 SWS (exercises)Credit points (B.Sc.): 3 LP (lectures) + 1 LP (exercises)

Exams and grading:diploma: oral exam by appointment, graded certificate forexercisesB.Sc: written exam at the end of semester, 30% of the finalgrade from exercises

Office hours: by appointmentCourse web page:http://www.cogsys.cs.uni-tuebingen.de/lehre/ss11/introd comp sec.html

Homework assignments

Meetings:Tue, 10:00–12:00 (ct), A301First meeting: 26.04

4 homework assignments to be solved individuallyEvaluation and grade:

diploma: a grade reflects the percentage of points acquired.B.Sc.: a grade contributes 30% to the final grade.

Bibliography

Dieter Gollmann.Computer Security.Wiley & Sons, 2006.

Ross Anderson.Security Engineering.Wiley & Sons, 2001.

Bruce Schneier.Secrets and Lies: Digital Security in a Networked World.Wiley & Sons, 2004. (fun to read)

A typical web application

Legitimate user

BrowserWebserver

Internet

Attack: interception of communication

Legitimate user

BrowserWebserver

Internet

Attacker

Credit card number

Security goal: confidentiality

Prevention of unauthorized reading of dataPrevention of unauthorized learning of informationPotential abuse scenarios:

Discovery of confidential information (e.g. details of a businesscontract)Discovery of authentication credentials (e.g. password sniffing)

Enforcement intruments:Symmetric or asymmetric cryptographyAnonymization techniques

A typical web application

Legitimate user

BrowserWebserver

Internet

Attack: identity spoofing

Legitimate user

BrowserWebserver

Internet

Fake webserver

Attacker

Security goal: authentication

Verification of an identity of a person or a computerPrerequisite for access controlAuthentication methods:

Shared secrets (e.g. password or PIN)Ticket systems (identity cards, digital certificates)Challenge-response techniquesBiometric techniquesHuman authentication: CAPTCHA’s, Turing test, etc.

Authentication risks: identity theft

A typical web application

Legitimate user

BrowserWebserver

Internet

Attack: injection of malicious code

Legitimate user

BrowserWebserver

Internet

Attacker

Malware

XSS attack

Security goal: integrity

Prevention of malicious tampering of dataPotential abuse scenarios:

Fraudulent modification of data (e.g. 100,000¤ instead of100¤ in an online transaction request)Injection of malicious code in downloaded softwareEvading detection by modification of a compromized operatingsystem

Enforcement instruments:Integrity checking using cryptographic hash functions

A typical web application

Legitimate user

BrowserWebserver

Internet

Attack: server overload

Legitimate user

Browser

Internet

Server overloaded

Security goal: availability

A joint objective of security and dependabilityMay be caused by attacks as well as natural phenomena,such as design errors or flash crouds.Enforcement instruments:

Detection of DoS-attacksRouter and firewall reconfigurationService redundancyVirtualization

A typical web application

Legitimate user

BrowserWebserver

Internet

Attack: transaction denial by a user

Legitimate user

BrowserWebserver

Internet

Credit card charded

Transaction cancelled

Security goal: accountability

An audit trail of security-related eventsA key instrument of detection/responseA stronger form of accountability is non-repudiation:unforgeable evidence that a certain action occurred.Similar attacks as integrityEnforcement instruments:

Integrity checksRead-only auditDigital certificates and trusted third parties

Summary

Security is not a solution but an ongoing process.Security can only be achieved by a combination of technicaland organizational measures.One of the biggest security risks is a user.Security is a big challenge but lots of fun as well: a greatfield of study and research.

Next lecture

The economics of computer securitySecurity threatsSecurity design principles