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- Systems Security: Part 1 - Prof. Dr. Michael Backes Director, - - PowerPoint PPT Presentation

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Introduction to Cybersecurity - Systems Security: Part 1 - Prof. Dr. Michael Backes Director, CISPA Center for IT Security, Privacy, and Accountability Chair for IT-security & Cryptography General Information Correct formatting

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SLIDE 1

Introduction to Cybersecurity

  • Systems Security: Part 1 -

Director, CISPA – Center for IT Security, Privacy, and Accountability Chair for IT-security & Cryptography

  • Prof. Dr. Michael Backes
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SLIDE 2

General Information

  • Correct formatting (Tutorial group 1, Exercise 1):

[1][Exercise 1]

1 Foundations of Cybersecurity 2016

  • No additional whitespaces! No <>!
  • New submission mail address to avoid confusion:

submissions-cysec16@cs.uni-saarland.de

  • Different prefix than regular mailing list
  • Old submission addresses still work
  • Exercise groups start on Wednesday
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SLIDE 3

Last Lecture

  • Organizational matters
  • Commercialization of cyber attacks
  • What is cyber security and what has to be protected
  • Hardware, software stack, crypto, network
  • Software exploits, hardware hacks, side-channels, …
  • Intro to cryptography
  • Ancient ciphers: Caesar, Substitution cipher, Vigenère cipher, Enigma
  • Cryptanalysis of ancient ciphers

2 Foundations of Cybersecurity 2016

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SLIDE 4

Part I: System Security

http://dilbert.com/strips/comic/2005-09-12/

Foundations of Cybersecurity 2016 3

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SLIDE 5

The Programmer’s Blues

4 Foundations of Cybersecurity 2016

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SLIDE 6

Heartbleed

  • Serious vulnerability in the popular OpenSSL

cryptographic software library

  • Missing bounds check before a memory

copy operation that uses non-sanitized user input as the length parameter

  • Not a crypto error, but an

implementation error!

  • Allows anyone on the Internet to read the

memory of the systems protected by the vulnerable versions of OpenSSL

  • Private keys
  • In-memory decrypted packets received

via SSL connection

  • Etc.

5 Foundations of Cybersecurity 2016

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SLIDE 7

How Heartbleed works

6 Foundations of Cybersecurity 2016

http://xkcd.com/1354/

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SLIDE 8

Chapter “System Security” Overview

  • This lecture:

Security Principles & Authentication

  • 2nd lecture:

Access Control & Malware

  • 3rd lecture:

Hijacking control flows

7 Foundations of Cybersecurity 2016

Hardware OS

Software

Crypto User

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SLIDE 9

Chapter “System Security” Overview

  • Practical security (How to exploit vulnerabilities?)
  • Security principles
  • Basic design of (in-)secure systems
  • Basics of access control, malware
  • How to hijack control in computer systems?
  • How to defend against such control hijacking attacks?
  • Authentication methods
  • Project: Learn about basic control-flow hijacking
  • Some advanced topics are part of follow-up lectures

(Security, Security Engineering)

8 Foundations of Cybersecurity 2016

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SLIDE 10

Recommended Literature

  • William Stallings, Lawrie Brown. “Computer Security: Principles and Practice.” ISBN-13: 978-0135137116 (third,

international edition)

  • Chapter 1: Overview
  • Chapter 3: Authentication
  • Chapter 4: Access Control
  • Only Sections 4.1-4.5
  • Chapter 6: Malicious Software
  • Chapter 10: Buffer Overflow
  • Chapter 13: Trusted Computing and Multilevel Security
  • Only Sections 13.1 and 13.3
  • David Basin, Patrick Schaller, Michael Schläpfer. “Applied Information Security: A Hands-On Approach.” ISBN:

978-3-642-43632-1

  • Chapter 1: Security Principles
  • Chapter 4: Authentication and Access Control
  • Chapter 6: Web Application Security
  • Jerome Saltzer, Michael Schroeder. “The Protection of Information in Computer System.” In Proceedings of the

IEEE, volume 63, pages 1278—1308, 1975

9 Foundations of Cybersecurity 2016

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SLIDE 11
  • Prof. Dr. Michael Backes

Security Principles

11.11.2016

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SLIDE 12

General Notions

  • Subject
  • Active entity (e.g., user or a system acting on behalf of a user)
  • Object
  • Passive entity (e.g., data container like files, directories, etc.)
  • General assumption: Access to an object gives access to the objects’ data

content (information)

  • Information is encoded/represented as various forms of data
  • Subject is Authorized: Allowed by security policy to access object

11 Foundations of Cybersecurity 2016

Object

(e.g., Resource like File)

Subject

(e.g., User process) If authorized: Accesses and operates on

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SLIDE 13

Refresher: Classic Information Security Goals

  • Confidentiality
  • Assure that information is not disclosed to unauthorized principals
  • Integrity
  • Data: Prevent unauthorized modification of programs and information
  • System: Assure that system performs its intended function in an unimpaired manner,

free from unauthorized manipulation

  • Availability
  • Guarantee reliable access to information and services by authorized principals
  • Further important goals:
  • Accountability: Trace actions of an entity uniquely back to that entity
  • Authenticity: Property of being genuine and being able to be verified and trusted
  • Privacy, Non-repudiation, Anonymity, Unlinkability
  • Depending on context, not always easy to define precisely
  • Sometimes contradicting and not easy to combine
  • Anonymity vs accountability

12 Foundations of Cybersecurity 2016

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SLIDE 14

12 Security Principles

  • High level goals
  • Security best practices
  • Applicability depends on concrete context
  • Especially applies to secure software design
  • Emphasizes clean and secure design
  • Often requires trade-offs

13 Foundations of Cybersecurity 2016

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SLIDE 15

14 Foundations of Cybersecurity 2016

https://cdn1.coolstuff.com/autogen/preset/aspectThumb/960x720/6305517763ac93f87c1e5babc5d657c7.jpg http://www.richter-spielgeraete.de/tl_system/content/de/01_Produkte/xx_Piktogramme/3.63390.gif

VS

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SLIDE 16

Simplicity

  • Applies to any engineering and implementation task:
  • The simpler the solution
  • the easier to understand, analyze, and review
  • less likely to contain flaws
  • Negative examples: Monolithic operating systems, browser, email clients

15 Foundations of Cybersecurity 2016

Keep it simple.

Linux kernel Firefox Chrome Win Xp OS X Tiger Thunderbird Bash

2 4 6 8 10 50 100 WEIGHTED CVSS SCORE LINES OF CODE (MILLIONS)

Linux kernel Firefox Chrome Win Xp OS X Thunderbird Bash

200 400 600 800 1000 1200 1400 50 100 # VULNERABILITIES LINES OF CODE (MILLIONS)

Sources: cvedetails.com

  • penhub.net
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SLIDE 17

16 Foundations of Cybersecurity 2016

http://www.surface-generation.com/wp-content/uploads/2015/03/Question-mark-box-620-x-350.jpg

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SLIDE 18

Open Design

  • Avoid “Security by obscurity”
  • In crypto a.k.a. Kerckhoffs’ principle
  • Security should depend on possession of secrets only (passwords, keys, …)
  • Simply not possible to maintain secrecy of a system that should be

distributed (e.g., reverse engineering)

  • Intuitive example: Securing a door does not rely on attacker’s ignorance to
  • perating a door, but on possession of the key and security of lock

mechanism

  • Today’s de-facto crypto mechanisms all developed with open design
  • Counter examples: DRM mechanisms (e.g. DVD, Playstation,…), KeeLoq,

Windows NT LAN Manager, Mifare classic (basis for old UdS card)

17 Foundations of Cybersecurity 2016

The security of a system should not depend on the secrecy of its protection mechanisms.

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SLIDE 19

18 Foundations of Cybersecurity 2016

http://uncrate.com/p/2008/03/oxo-pop-containers.jpg

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SLIDE 20

Compartmentalization

  • Groups (or compartments) isolated from each other with limited communication between compartments over

controlled channel

  • Facilitates simplification of design (“divide-and-conquer” approach); attacks or errors contained to affected

compartment; security-sensitive functionality can be in dedicated hardened compartment

  • Compartmentalization at different levels:
  • User-space vs kernel space
  • Memory space (between processes; data vs code)
  • Modularization of software
  • µKernel
  • Virtual machines
  • Network zones
  • Problem: Not always possible to completely isolate

resources/functionality

  • Tightly control channel between compartments

and compartment interfaces

  • Intuitive Example:

Compartmentalized submarine design

  • Example: µKernel vs monolithic kernel

19 Foundations of Cybersecurity 2016

Organize resources into isolated groups of similar needs.

System

Network User input File system Network User device File system Network User input File system Network User display File system

Monolithic design µKernel with compartmentalization

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SLIDE 21

20 Foundations of Cybersecurity 2016

https://www.google.de/maps/@48.8547067,2.3438011,17z

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SLIDE 22

Minimum Exposure

  • Reduce external interfaces to a minimum
  • E.g., network-listening services
  • f a computer system
  • Limit amount of information given away that can help an adversary
  • E.g., error pages of webservers provide

information about the software versions

  • Minimize the window of opportunity for an adversary to attack
  • E.g., limit the number of failed password

attempts before locking account

21 Foundations of Cybersecurity 2016

Minimize the attack surface a system presents to the adversary.

http://articles.slicehost.com/assets/2008/12/5/apache-404-footer.jpg http://cache.clickonf5.org/wp-content/uploads/2009/12/twitterlocked_thumb.png http://www.bryanandrews.org/wp-content/uploads/2001/11/nmap-banner-scan-example.png

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SLIDE 23

22 Foundations of Cybersecurity 2016

http://melaniejor.typepad.com/.a/6a00e54fd1fc4388340133f2f9498f970b-pi http://www.keyring.com/images/products/detail/92400_Split_key_ring.jpg http://thumbs.dreamstime.com/t/blue-house-22708798.jpg http://cliparts.co/cliparts/qcB/X7G/qcBX7Ga4i.jpg

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SLIDE 24

Least Privilege

  • What is a ‘privilege’?
  • Ability to access or modify a resource (e.g., file, hardware, networking)
  • Privileged process: Process that has access to some resource not generally available
  • More secure systems have many types of privilege
  • Why?
  • Obvious reason: A malicious or compromised process cannot misuse privileges that it does

not have!

  • Compartmentalization helps realizing least privilege
  • Delegation of tasks to sufficiently privileged processes, but requires careful design of

programs to avoid “confused deputy attacks”

  • Implementation often difficult: Requires detailed understanding of system and all possible
  • perations and dependencies
  • Examples towards least privilege: user accounts vs guest accounts vs administrative

accounts, Android permission framework

23 Foundations of Cybersecurity 2016

Any component (and user) of a system should operate using the least set of privileges necessary to complete its job.

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SLIDE 25

24 Foundations of Cybersecurity 2016

https://s-media-cache-ak0.pinimg.com/736x/fb/be/d9/fbbed9c16f8422d0d3febecd55ed98f4.jpg

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SLIDE 26

Minimum Trust and Maximum Trustworthiness

  • Trusted system: User assumes that system will behave as expected, but system may misbehave

(in particular by acting maliciously)

  • Trust should be avoided when possible
  • Trustworthy system: System always acts as expected by user
  • Minimizing trust = minimizing expectations about the system

(can result in complete loss of trust into a system)

  • Maximizing trustworthiness = turning assumptions into validated properties (e.g., rigorously

prove that system behaves only in expected manner)

  • Example: Program receiving user input
  • Never trust the user input! (minimize trust)
  • Always validate and filter user input! (maximize trustworthiness)
  • Problem: Transitive trust (‘chain of trust’)
  • A → B, B → C, thus A → C (possibly unknown to A)
  • Complicates completely reasoning about security of an entity (e.g. A)

25 Foundations of Cybersecurity 2016

Minimize trust and maximize trustworthiness.

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SLIDE 27

26 Foundations of Cybersecurity 2016

http://www.gmesupply.com/images/1/gme-supply_0135s.jpg

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SLIDE 28

Secure, Fail-Safe (Fail-Secure) Defaults

  • System designed to prevent unsafe/insecure consequences of the system's

failure

  • Requires that system starts in a secure state
  • Important in access control
  • Identify conditions under which access is granted
  • Default case: If conditions are not fulfilled, deny access (whitelisting)
  • Fail securely: Conditions wrongly identified → Access denied (wrongly)

27 Foundations of Cybersecurity 2016

The system should start in a secure state and return to a secure state in the event of a failure.

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SLIDE 29

28 Foundations of Cybersecurity 2016

http://resources0.news.com.au/images/2013/09/11/1226716/529036-airport-security-tsa-screeners.jpg

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SLIDE 30

Complete Mediation

  • Requires that the access control mechanism encompasses all security-

relevant objects and is operational in any system state

  • Access control must not be circumventable
  • To mitigate attacks at layers below the access control mechanisms, data

should be additionally be protected in transit and storage (e.g., encryption)

  • Example lower-layer attacks: booting a different operating system like a

live CD to circumvent access control or sniffing web traffic

  • Requires authentication to securely identify subjects and objects of any

access

29 Foundations of Cybersecurity 2016

Access to any object must be monitored and controlled.

Object

(e.g., Resource like File)

Subject

(e.g., User process)

access request

Monitor

If authorized

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SLIDE 31

30 Foundations of Cybersecurity 2016

http://www.i2clipart.com/clipart-wall-c7b9

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SLIDE 32

No Single Point of Failure

  • Also known as “defense in depth”: Do not rely on a single security mechanism
  • If one mechanism fails, another should prevent malice
  • How many security layers?
  • Depends on cost-benefit analysis: performance requirements, usability

aspects, administrative overhead, etc.

  • How?
  • Common technique: Separation of duties
  • More than one entity/mechanism required to complete a task
  • Several examples in physical world

(one letter with credit card, separate letter with PIN; airplane with four instead of two engines; high security safes with two locks and keys held by different guards;…)

31 Foundations of Cybersecurity 2016

Build redundant security mechanisms whenever feasible.

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SLIDE 33

32 Foundations of Cybersecurity 2016

http://www.tradersmessageboards.com/wp-content/uploads/2015/06/print-audit-300x300.png

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SLIDE 34

Traceability

  • Trace: Sign or evidence of past events
  • Traceability: System retains traces of activities (i.e., record of sequence of

events from which history of system can be reconstructed)

  • Important for accountability
  • Link actions to a subject that can be held responsible
  • Usually implemented through logging
  • Logs must be protected to prevent adversary from removing his traces
  • Can contradict privacy requirements
  • Possible solution: Use of pseudonyms, store true identities separately

(→ Separation of duties for tracing events of a true identity)

33 Foundations of Cybersecurity 2016

Log security-relevant system events.

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SLIDE 35

34 Foundations of Cybersecurity 2016

https://xkcd.com/221/

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SLIDE 36

Generating Secrets

  • Entropy in information theory (coll.): “Degree of randomness”
  • High entropy of secrets (e.g., crypto keys, passwords, etc) required to prevent

simple guessing or brute-forcing attacks

  • “Helps keeping secrets secret”
  • Debian OpenSSL PRNG bug: Random number generator code was

“optimized” → RNG became predictable → Cryptographic key material generated with this RNG became predictable → SSL on Debian was broken

35 Foundations of Cybersecurity 2016

Maximize the entropy of secrets.

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SLIDE 37

36 Foundations of Cybersecurity 2016

http://www.searchenginepeople.com/wp-content/uploads/2012/05/bad-usability.jpg

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SLIDE 38

Usability

  • Security mechanisms should be easy to use
  • The harder the security mechanism is to use, the more likely it is that users

(or developers/administrators) will circumvent it or will apply it incorrectly

37 Foundations of Cybersecurity 2016

Design usable security mechanisms.

  • Examples:
  • Alma Whitten, J.D Tygar. “Why Johnny

Can’t Encrypt: A Usability Evaluation of PGP 5.0”: Majority of test users were unable to encrypt an email

  • Sunshine et al. “Crying wolf: an empirical

study of SSL warning effectiveness”: SSL/TLS warnings ineffective

  • Recent works on Android: Alarmingly high

number of app developers do not verify SSL certificates correctly, opening their app to network attacks

From https://www.usenix.org/legacy/events/sec09/tech/slides/sunshine.pdf

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SLIDE 39

Authentication

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SLIDE 40

Authentication: Basic notions

  • Identification is whom you claim to be
  • Authentication is how you prove your ID
  • Credentials: Evidence used to prove the ID
  • Usually a prerequisite for authorization to use system resources
  • Forms of authentication
  • Something you know

(e.g., a password)

  • Something you have

(e.g., smart card, TAN generator)

  • Something you are

(e.g., fingerprint)

  • Combination of those above

(e.g., two-factor authentication for online banking)

39 Foundations of Cybersecurity 2016

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SLIDE 41

Password authentication

  • Most common authentication method
  • Basic idea
  • User has a secret password
  • System checks password to authenticate user
  • Issues?
  • How is password stored?
  • How does system check password?
  • How easy is it to guess a password?
  • Difficult to keep password file secret, so best if it is hard to guess password even if

you have the password file

  • “Passwords are like underwear”
  • … change them regularly
  • … don’t share them with friends or strangers
  • … don’t leave yours lying around

40 Foundations of Cybersecurity 2016

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SLIDE 42

Basic password scheme

41 Foundations of Cybersecurity 2016

Password file

User exrygbzyf kgnosfix ggjoklbsz … … frunobulax

hash function

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SLIDE 43

Detour: Hash functions (high-level)

  • Simplified definition (more in crypto part):

hash_function(arbitrary length input) → fixed length output

  • Illustrative (bad!) example:

𝑦 ∈ ℕ, ℎ𝑏𝑡ℎ 𝑦 → ቊ0 𝑗𝑔 𝑦 𝑗𝑡 𝑓𝑤𝑓𝑜 1 𝑗𝑔 𝑦 𝑗𝑡 𝑝𝑒𝑒

  • Cryptographic hash functions have ideally the following properties
  • One-way functions
  • Easy to compute output from input, infeasible to compute input from output
  • Collision-resistance
  • Infeasible to find two different inputs that compute to the same output

42 Foundations of Cybersecurity 2016

Input space Output space Collisions {0,1}

ℕ

???

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SLIDE 44

Basic password scheme

  • Cryptographic hash function h: strings  strings
  • Given h(password), hard to find password
  • No known algorithm better than trial and error
  • User password stored as h(password)
  • When user enters password
  • System computes h(password)
  • Compares with entry in password file
  • No plaintext passwords stored on disk

43 Foundations of Cybersecurity 2016

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SLIDE 45

Example: Unix password system

  • Structure of password entry:

username:$id$salt$h(salt|password)$

  • $: Separator between entry fields
  • id: identifies the algorithm h used to compute h(salt|password)
  • Examples: 1: md5, 5: SHA-256, 6: SHA-512
  • Not a plain hash, but several iterations (≈5000) to slow down offline attacks

[http://www.akkadia.org/drepper/SHA-crypt.txt]

  • salt: makes dictionary attacks harder
  • |: concatenation operator
  • Password file is publicly readable
  • Any user can try “offline dictionary attack”
  • User looks at password file
  • Computes h(word) for every word in dictionary; if result matches entry in

password file, user found a valid password for user

44 Foundations of Cybersecurity 2016

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SLIDE 46

Dictionary Attack – Some numbers

  • Kali Linux dictionary (popular pentesting distribution)
  • Contains database with 14,344,392 entries of common passwords
  • Names, popular passwords, passwords leaked earlier from websites and services
  • hashcat tool can test ≈16K salted UNIX SHA-512 passwords per second on a good

workstation

  • Testing complete dictionary a matter of minutes
  • GPU-based oclHashcat tool can even test up to billions of hashes per second on small GPU clusters
  • Dedicated hardware and large GPU clusters (e.g. for bitcoins) can test billions to trillions of hashes

per second [https://en.bitcoin.it/wiki/Mining_hardware_comparison]

  • Dimensions of password strength: length × size of character set × randomness of characters
  • If passwords were completely random and uniformly distributed
  • Assume six-character password
  • Upper- and lowercase letters, digits, 32 punctuation characters
  • 946 = 689,869,781,056 possible passwords
  • Exhaustive search (“brute force”) using above machine and hashcat requires ≈250 days on average
  • Problem with truly random passwords: Hard to remember

45 Foundations of Cybersecurity 2016

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SLIDE 47

Example: hashcat to ‘recover’ salted Unix passwords from dictionary

bugiel@Colossus01:~/hashcat-0.47$ cat pw.hash $6$kbA7uCaJ$jSN6v19v8Mj6qqzsi85A/9IG3d4CDzMkY1KxiwoM2BxPS8dqL5wg.DZrOuiHF3OX/6c/b0DoZQTPphptZxx4o. $6$BhvJ.qe2$IopPfOUpXfNX82.rK9g8rqLwutjOaqxFwuVdqWefBNs7JgWPIerp..JSj2khiu9qsW3M0FcMmuB0jrcXvZwHH1 bugiel@Colossus01:~/hashcat-0.47$ ./hashcat-cli64.bin -m 1800 -a 0 -o cracked.txt --remove \ pw.hash ~/rockyou.txt -n 32 All hashes have been recovered Input.Mode: Dict (/home/bugiel/rockyou.txt) Index.....: 5/5 (segment), 541142 (words), 5720149 (bytes) Recovered.: 2/2 hashes, 2/2 salts Speed/sec.: - plains, 6.68k words Progress..: 540718/541142 (99.92%) Running...: 00:00:01:20 Estimated.: --:--:--:-- Started: Tue Sep 9 14:41:23 2014 Stopped: Tue Sep 9 15:20:45 2014 bugiel@Colossus01:~/hashcat-0.47$ cat cracked.txt $6$kbA7uCaJ$jSN6v19v8Mj6qqzsi85A/9IG3d4CDzMkY1KxiwoM2BxPS8dqL5wg.DZrOuiHF3OX/6c/b0DoZQTPphptZxx4o. :ilovebeer $6$BhvJ.qe2$IopPfOUpXfNX82.rK9g8rqLwutjOaqxFwuVdqWefBNs7JgWPIerp..JSj2khiu9qsW3M0FcMmuB0jrcXvZwHH1 :!!!lollipop!!!

46 Foundations of Cybersecurity 2016

slide-48
SLIDE 48

Salting

  • Salting:

[Alice, saltA, h(passwordAlice || saltA)], [Bob, saltB, h(passwordBob || saltB)], …

  • Salt is random for every user
  • Linux – 8 characters for salt (max. 16)
  • Assume charset [a-zA-Z0-9./] for salt (64 possible characters):

648 = 281,474,976,710,656 = 248 possible hashes of same password when salted

47 Foundations of Cybersecurity 2016

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SLIDE 49

Advantages of salt

  • Without salt
  • Same hash functions on all machines
  • Pre-compute hash of all common strings once
  • Compare hash file with all known password files
  • “Break once, break everywhere”-condition
  • With salt
  • One password hashed 248 different ways (8 character salt)
  • Pre-compute hash file?
  • Need much larger file to cover all common strings

(248 pre-computed hashes per possible password  storage problem)

  • Dictionary attack on known password file
  • For each salt found in file, try all common strings
  • Important: Salt like password hash are publicly readable

48 Foundations of Cybersecurity 2016

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SLIDE 50

Other countermeasures

  • Scenario: Offline attacks
  • Attacker has password file/database and can apply tools like hashcat
  • Increase complexity of hash computation to slow down attacker’s guessing

rate

  • E.g., cascade hashing: h(h(h(…..(h(password)))…)
  • Key stretching (e.g., PBKDF2)
  • Protect password file/database (e.g., encryption, access control,…)
  • Scenario: Online attacks
  • Attacker must enter password into a form to check current guess (e.g., login

screen)

  • Login mechanism can apply reactive measures:
  • Increasing timeout between two guesses
  • Lock account after number of wrong guesses
  • Proof that you are human (e.g., CAPTCHA)
  • Require second factor authentication (e.g., token)

49 Foundations of Cybersecurity 2016

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SLIDE 51

Reusable Passwords

  • People tend to reuse the same passwords in different places
  • If one site is compromised, the password can be stolen and used elsewhere
  • At the root of “phishing” attacks
  • Password managers
  • Allow complex, long, unique password per account
  • Store password in an encrypted file
  • Potential single point of failure: Who can see this file? How strongly is it

protected? Can malware get at the database?

  • People use multiple machines
  • Synchronize the password database?
  • Managers that can securely recognize websites can help protect against

phishing

50 Foundations of Cybersecurity 2016

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SLIDE 52

Recall: Phishing

51 Foundations of Cybersecurity 2016

Looks normal...

…but is not!

slide-53
SLIDE 53

Safe to type your password?

52 Foundations of Cybersecurity 2016

slide-54
SLIDE 54

Safe to type your password?

53 Foundations of Cybersecurity 2016

slide-55
SLIDE 55

Safe to type your password?

54 Foundations of Cybersecurity 2016

slide-56
SLIDE 56

Safe to type your password?

55 Foundations of Cybersecurity 2016

???

slide-57
SLIDE 57

Safe to type your password?

56 Foundations of Cybersecurity 2016

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SLIDE 58

Safe to type your password?

57 Foundations of Cybersecurity 2016

http://www.threattracksecurity.com/it-blog/wp-content/uploads/2013/07/fakewiki1.jpg

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SLIDE 59

Tool support for Phishers

58 Foundations of Cybersecurity 2016

10 seconds of work with the setoolkit (social engineering toolkit) Real

slide-60
SLIDE 60

Guessable passwords

September 16, 2008:

  • Compromise of gov.palin@yahoo.com using

password-reset functionality of Yahoo Mail.

  • No secondary mail needed
  • Date of Birth – Wikipedia
  • Zipcode – Wasilla has two
  • Where did you meet your spouse?
  • Biographie
  • Wikipedia, again…
  • Google
  • Successfully changed

password to “popcorn”

59 Foundations of Cybersecurity 2016

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SLIDE 61

Data Mining

  • Manufacturer of your first car?
  • Until 1998, Ford had >25% of market
  • First name of your best friend?
  • 10% of males: James/Jim,

John, Robert/Bob/Rob

  • Name of your first / favorite pet
  • Max, Jake, Buddy, Bear… etc.
  • Top 500 (covers 65% of names)

is available online

  • Mother’s Maiden Name, Social Security Number
  • “Messin’ with Texas”

[Griffith & Jakobsson, 2005]

60 Foundations of Cybersecurity 2016

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SLIDE 62

Guessable passwords

  • Wordhound: This is a tool that allows for the automated and targeted

construction of wordlists and dictionaries [based on Twitter data and web contents] for use in conjunction with password attacks.

[https://bitbucket.org/mattinfosec/wordhound]

  • CeWL: creating custom word lists by spidering a targets website and

collecting unique words [https://digi.ninja/projects/cewl.php]

61 Foundations of Cybersecurity 2016

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SLIDE 63

Guessable passwords

62 Foundations of Cybersecurity 2016

slide-64
SLIDE 64

Targeted attacks

  • If the attacker really wants your password

63 Foundations of Cybersecurity 2016

http://xkcd.com/538/ “Rubber hose cryptanalysis:” Coercion attack where the user is forcibly asked by an attacker to reveal the key

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SLIDE 65

Security research du jour

  • Neuroscience Meets Cryptography:

Designing Crypto Primitives Secure Against Rubber Hose Attacks

[Bojinov et al., USENIX Security Symposium 2012]

  • Use concept of implicit learning from cognitive psychology:

user learns patterns without any conscious knowledge of the learned pattern

  • Authors crafted a computer game to plant a password in the user’s brain without the user having

conscious knowledge of the trained password

  • Trained password can be used for authentication
  • But: No rubber hose attack, since user does not have conscious knowledge of password!
  • Cracking-Resistant Password Vaults using Natural Language Encoders

[Chatterjee et al., IEEE Security & Privacy 2015]

  • Problem: Master password of password vaults (or managers) is single point of failure,

attackable with efficient offline attacks

  • Authors built encrypted vaults that resist such offline cracking attacks and forcing attackers

to move to an online attack

  • Introduce a new type of secure encoding scheme that they call natural-language encoders (NLEs)
  • When decrypted with the wrong master password, it produces plausible-looking decoy passwords
  • Attacker must test actual passwords to check if guessed correct master password (i.e. online attack)

64 Foundations of Cybersecurity 2016

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SLIDE 66

Biometrics

  • Use a person’s physical characteristics
  • fingerprint, voice, face, keyboard timing, …
  • Advantages
  • Cannot be disclosed, lost, forgotten
  • Disadvantages
  • Cost, installation, maintenance
  • Reliability of comparison algorithms
  • False positive: Allow access to unauthorized person
  • False negative: Disallow access to authorized person
  • Privacy?
  • If forged, how do you revoke?

65 Foundations of Cybersecurity 2016

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SLIDE 67

Voluntary finger cloning

  • Select the casting material
  • Softened, free molding plastic (used by Matsumoto)
  • Part of a large, soft wax candle (used by Willis; Thalheim)
  • Push the fingertip into the soft material
  • Let material harden
  • Select the finger cloning material
  • Gelatin: “gummy fingers”, used by Matsumoto
  • Silicone: used by Willis; Thalheim
  • Pour a layer of cloning material into the mold
  • Let the clone harden

66 Foundations of Cybersecurity 2016

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SLIDE 68

Matsumoto’s Technique

67 Foundations of Cybersecurity 2016

Press a live finger against it. Only a few dollars’ worth of Materials Put the plastic into hot water to soften it. The mold

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SLIDE 69

Involuntary cloning

  • Clone without victim knowledge or assistance
  • Appears in Hollywood movies
  • Sneakers (1992) “My voice is my passport”
  • Never Say Never Again (1983) cloned retina
  • Charlie’s Angels (2000)
  • Fingerprints from beer bottles
  • Eye scan from oom-pah laser
  • Bad news: it works!
  • Chaos Computer Club: “Der Abdruck wurde durch CCC-Aktivisten von einem

Wasserglas sichergestellt, das Dr. Schäuble bei einer öffentlichen Veranstaltung benutzt hatte.” [http://www.ccc.de/en/updates/2008/schaubles-finger]

68 Foundations of Cybersecurity 2016

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SLIDE 70

Gummy finger from latent print

  • Capture clean, complete fingerprint on a glass, CD, or other smooth, clean surface
  • Pick it up using tape and graphite
  • Scan it into a computer at high resolution
  • Enhance the fingerprint image
  • Print with laser printer
  • Overlay print with wood glue
  • After drying, your new identity is ready

69 Foundations of Cybersecurity 2016

Source: http://dasalte.ccc.de/biometrie/fingerabdruck_kopieren.de

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SLIDE 71

Security research du jour

  • Continuous authentication using biometrics
  • Problem: One-time authentication (e.g. login screen) becoming insufficient on modern

devices

  • PCs/Laptops often left unattended but logged in!
  • Smartphones require high frequency of unlocking. Too cumbersome for many users, which

thus do not set a password or lock pattern! (Usability principle not fulfilled)

  • Continuous authentication: Seamless (re-)authentication of the user’s identity
  • Various research works based on biometrics
  • Examples:
  • How you type text on a keyboard (typing activity)
  • How you interact with the touchscreen of smartphone (type/swipe

frequency/acceleration/trajectory/pressure, rotation of the phone during interaction)

  • User’s gait (detected using smartphone sensors)
  • Fingerprint scanner integrated in mouse
  • Usually rely on machine learning (neural networks)

70 Foundations of Cybersecurity 2016

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SLIDE 72

Token-based authentication

  • Several configurations and modes of use
  • Device produces password, user types into system
  • User unlocks device using PIN
  • User unlocks device, enters challenge
  • Example: S/Key
  • User enters string, device computes sequence
  • p0 = hash(string|rand); pi+1 = hash(pi)
  • pn placed on server; set counter k = n
  • Device can be used n times before reinitializing
  • Send pk-1 = to server, set k = k-1
  • Sever checks hash(pk-1) = pk , stores pk-1

71 Foundations of Cybersecurity 2016

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SLIDE 73

Disadvantages of Tokens

  • Can be stolen or lost
  • Lack of hardware/software support on many machines
  • Inconvenient to use
  • Cost

72 Foundations of Cybersecurity 2016

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SLIDE 74

Two-Factor Authentication

  • Combine two of the three types of authentication
  • Use second factor to work around limitations of first
  • Important security requirement:

Both channels are independent from each other, so compromise of one channel does not compromise the other

  • Examples:
  • Online banking password plus generated TAN
  • Online banking password plus mTAN

(unless banking done on same phone that receives mTAN)

  • Account password plus authenticator
  • RSA SecurID card plus PIN

73 Foundations of Cybersecurity 2016

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SLIDE 75

Security research du jour

  • Sound-Proof: Usable Two-Factor Authentication Based on Ambient Sound

[Karapanos et al. USENIX Security Symposium 2015]

  • Problem: Usability issues of two-factor authenticaton
  • Authors use proximity of the user’s phone to the device being used to log in as

second factor

  • proximity of the two devices is verified by comparing the ambient noise recorded by

their microphones

  • Audio recording and comparison are transparent to the user, so that the user

experience is similar to one-factor authentication (e.g., password only)

  • The Sounds of the Phones: Dangers of Zero-Effort Second Factor Login based on

Ambient Audio

[Shrestha et al. Conference on Computer and Communications Security 2016]

  • Attack on Sound-Proof
  • Emit predictable sound from smartphone (alert, call, media playback, …)

74 Foundations of Cybersecurity 2016