Introduction to Computer and Network Security | CS 475, Study notes of Cryptography and System Security

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CS475: Lecture 1

Computer and Network

Security

Rachel Greenstadt January 6, 2009

Introductions

Your name

Year at drexel

Why interested in Computer Security and CS 475?

Something else interesting about you

Overview

Current events in “Computer and Network Security”

The Computer In security Industry

About CS 475

What is security?

What is “Computer and Network Security”

Write down your answers and swap with a neighbor

The Internets Are

Broken: Part 1 DNS

maps names to ip addresses

www.drexel.edu 144.118.31.

distributed: root server delegates to .edu server delegates to drexel.edu server

don’t want badhacker.drexel.edu answering for www.drexel.edu

supposed to be solved by transaction ID (# btwn 0 and 65535 that real server knows, others don’t)

DNS Attack

• Once an answer is received it is cached for TTL (usually one day)
• 1 day * 65,536 lookups / 2 = 84.5 years for 50% chance (not exactly)
• Four observations by Dan Kaminsky

Bad guy doesn’t have to look anything up, so replies first (if right TXID)

Bad guy can try numbers until good guy returns (maybe 100?)

TTL only stops lookups for www.foo.com, not random other names like name1.foo.com, name2.foo.com, etc

name83.foo.com can win www.foo.com by delegating his answer to www.foo.com at some wrong address (6.6.6.6)

The Internets are

Broken: Part 11 MD

via: Alexander Sotirov, Marc Stevens, Jacob Appelbaum, Arjen Lenstra, David Molnar, Dag Arne Osvik, Benne de Weger How ssl web security is supposed to work

Creating a Rogue CA

Hash collisions in MD

2007 chosen prefix collision for MD

can put collision bits in the key for the cert (supposed to look random)

some more complications (some parts of the cert are specified by the CA, but they were able to guess these)

Crypto is hard:

Diffie-Hellman

Alice Bob EBob(g x ) g y , H(K) K= g xy This depends on the hardness of discrete log (hard to find x from g x ) Now both sides have a symmetric key, K= g xy , Why do we need to encrypt g x ? Why do we need H(K)? What’s still broken?

Crypto is hard: Debian

The following lines were removed from md_rand.c

valgrind and purify (useful debugging tools) complained about uninitialized memory

As a result, randomness in debian generated keys (SSL and SSH) was reduced to 15 bits (32, unique keys) and cryptographic ops were suspect MD_Update(&m,buf,j); [ .. ] MD_Update(&m,buf,j); /* purify complains */

Software Sucks : Part 1

7,000-8,000 vulnerabilities per year (CERT)

Leveled off after 2006, but

malware and trojans increased 300% 2007 (according to microsoft)

Increasing vectors web 2.0 (esp wordpress), online games

Data Protection

doesn’t exist

Data aggregators compile in-depth dossiers on everyone

Choicepoint sold 163,000 record to identity thieves in 2005

Often this data is lost, stolen, or misused

Privacy Rights Clearinghouse documents the loss of 246,134,559 sensitive records since 2005

SQL Injection

This sort of attack on the rise in 2008...mostly attacking web sites