INternet SECURITY - IIT Bombaysiva/talks/secnet.pdf · 3. garbo-vsnl-radio.iitb.ac.in 0% 21 21 0 0...

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INternet SECURITYG. Sivakumar

Computer Science DepartmentIndian Institute of Technology, Bombay

Mumbai 400076, [email protected]

Outline of Talk

• Internet and Security Overview

• Security Requirements, Threats and Mechanisms

• Cryptographic Protocols and Attacks

– Session Key Establishment

– Mutual Authentication

• Site Security Planning and Implementation

• Q&A

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Power of Networking

• Knowledge is Power

• Issac Newton– “... stood on the shoulders of giants.”

• ...

• Are there no bad aspects ofnetworking?

• If yes, no need for this lecture!

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Internet’s Dream

• Why should a fridge be on Internet?

• Will security considerations make this anightmare?

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Internet’s Growth andCharter

InformationAnyTime, AnyWhere, AnyForm, AnyDevice, ...WebTone like DialTone

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Security Concerns onInternet

Sample problems

• Highly contagious viruses

• Defacing web pages

• Credit card number theft

• On-line scams

• Intellectual property theft

• Wiping out data

• Denial of service

• Spam E-mails

• Reading private files

• Surveillance

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Who are the attackers?• Unintended blunders

• Hackers driven by technical challenge

• Disgruntled employees or customers

• Petty criminals

• Organized crime

• Organized terror groups

• Foreign espionage agents

• Information warfare

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Recent Top 10 AttacksSeewww.securityfocus.comandwww.sans.orgfor more details

1. Nimda Worm (IIS/MIME bugs)

2. Code Red Worm (Buffer Overflow)

3. Code Red II Worm

4. Spam Mail (Open Relays/Formmail)

5. CGI Attacks

6. SubSeven Trojan

7. Microsoft FrontPage Attacks

8. DNS Attacks

9. FTP Attacks

10. SSH CRC-32 Compensation Detection Attack

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Nimda and friendsNimda exploits

1. Microsoft IIS/PWS Escaped Characters Decoding Command ExecutionVulnerability

2. Microsoft IE MIME Header Attachment Execution Vulnerability

3. Microsoft IIS and PWS Extended Unicode Directory Traversal Vulnerabil-ity

4. Microsoft Office 2000 DLL Execution Vulnerability

and spreads itself via E-mail, Web-server attack, Web-browser code, Open Net-work Shares.

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Effect of Nimda, Code Red

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Common Vulnerabilities andExposures

Seecve.mitre.org.A nomenclature(and database) for indexing vulnerabilites. Critical to evaluatevarious approaches/tools.

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Security RequirementsInformal statements (formal is much harder)

• ConfidentialityProtection from disclosure to unauthorized persons

• IntegrityAssurance that information has not been modified unauthorizedly.

• AuthenticationAssurance of identity of originator of information.

• Non-RepudiationOriginator cannot deny sending the message.

• Availability Not able to use system or communicate when desired.

• Anonymity/PseudonomityFor applications like voting, instructor evalua-tion.

• Traffic AnalysisShould not even know who is communicating with whom.Why?

• Emerging ApplicationsOnline Voting (more later)

And all this with postcards (IP datagrams)!

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What is a ComputerNetwork?

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So, what’s Internet?• A bottom-up collection (interconnection) of networks

• TCP/IP is theonly common factor

• Bureaucracy-free, reliable, cheap

• Decentralized, democratic, chaotic

• Internet Society (www.isoc.org)

• Internet Engineering Task Force (www.ietf.org)

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Why is Internet Vulnerable?Quick overview of how Internet works.

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TRACEROUTEPackets Pings

Hostname %Loss Rcv Snt Last Best Avg Worst1. 192.168.106.129 0% 21 21 0 0 0 12. 144.16.122.100 0% 21 21 1 1 3 213. garbo-vsnl-radio.iitb.ac.in 0% 21 21 0 0 0 34. router-vsnl-radio.iitb.ac.in 0% 21 21 1 1 1 25. 203.197.31.154 0% 21 21 2 2 3 136. 203.197.33.129 0% 21 21 2 2 3 167. lvsb-vsb-stm-1.Bbone.vsnl.net.in 0% 21 21 3 2 3 58. 64.86.90.137 0% 21 21 479 206 349 5889. if-0-0.bb8.NewYork.teleglobe.net 0% 21 21 206 205 207 217

10. sl-gw9-nyc-7-0.sprintlink.net 0% 21 21 206 205 207 22011. sl-bb26-nyc-15-2.sprintlink.net 0% 21 21 206 206 207 21112. sl-bb27-nyc-8-0.sprintlink.net 0% 21 21 206 206 210 25613. sl-bb24-nyc-8-0.sprintlink.net 0% 21 21 206 206 207 21714. 144.232.9.118 0% 21 21 207 206 207 22015. dcr1-loopback.SantaClara.cw.net 0% 20 21 293 293 294 29616. ibr01-p5-0.sntc05.exodus.net 0% 20 21 295 294 295 30517. bbr02-g2-0.sntc05.exodus.net 0% 20 21 295 294 295 29918. bbr01-p7-0.sntc03.exodus.net 0% 20 21 294 294 295 30119. dcr04-g4-0.sntc03.exodus.net 0% 20 20 295 295 296 31620. csr01-ve241.sntc03.exodus.net 10% 18 20 307 295 305 44121. google-exodus.exodus.net 0% 20 20 303 294 295 30322. exbi2-1-1.net.google.com 0% 20 20 297 296 300 32023. www.google.com 0% 20 20 295 295 296 304

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Vulnerabilities• Application Security

– Buggy code

– Buffer Overflows

• Host Security

– Server side (multi-user/application)

– Client side (virus)

• Transmission Security

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Windows Top 10Vulnerabilities

Seehttp://www.sans.orgfor more info (CVE numbers, how to check/protectetc.)

1. Internet Information Services (IIS)

2. Microsoft Data Access Components (MDAC) (Remote Data Services)

3. Microsoft SQL Server

4. NETBIOS – Unprotected Windows Networking Shares

5. Anonymous Logon – Null Sessions

6. LAN Manager Authentication – Weak LM Hashing

7. General Windows Authentication – Accounts with No (or Weak) Pass-words

8. Internet Explorer

9. Remote Registry Access

10. Windows Scripting Host

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Unix Top 10 VulnerabilitiesSeehttp://www.sans.orgfor more info (CVE numbers, how to check/protectetc.)

1. Remote Procedure Calls (RPC)

2. Apache Web Server

3. Secure Shell (SSH)

4. Simple Network Management Protocol (SNMP)

5. File Transfer Protocol (FTP)

6. R-Services (.rhosts) – Trust Relationships

7. Line Printer Daemon (LPD)

8. Sendmail

9. BIND/DNS

10. General Unix Authentication – Accounts with No or Weak Passwords

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Denial of Service:Real-world

Small shop-owner versus Supermarket

• What can the attacker do?

• What has he gained or compromised?

• What defence mechanisms are possible?

– Screening visitors using guards (who looks respectable?)

– VVIP security, but do you want to be isolated?

• what is the Internet equivalent?

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Yahoo DDoS attack• Caused traffic to Yahoo to zoom to 100s of Mbps

• Broke the capacity of machines at Yahoo and its ISPs

• Internet Control Message Protocol (ICMP) normally used for good pur-poses.

• Ping used to check “are you alive?’

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Yahoo DDoS attack

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Security Mechanisms• System Security:“Nothing bad happens to my computers and equipment”

virus, trojan-horse, logic/time-bombs, ...

• Network Security:

– Authentication Mechanisms“you are who you say you are”

– Access ControlFirewalls, Proxies “who can do what”

• Data Security: “for your eyes only”

– Encryption, Digests, Signatures, ...

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Cryptography and DataSecurity

• sine qua non[without this nothing :-]

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Symmetric/Private-KeyAlgorithms

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Asymmetric/Public-KeyAlgorithms

• Keys are duals (lock with one, unlock with other)

• Cannot infer one from other easily

• How to encrypt? How to sign?

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One way Functions

Mathematical Equivalents

• Factoring large numbers (product of 2 large primes)

• Discrete Logarithms

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Network SecurityMechanism Layers

Crptograhphic Protocolsunderly all security mechanisms. Real Challenge todesign good ones forkey establishment, mutual authenticationetc.

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Motivation for Session keysCombine Symmetric (fast) and Asymmetric (very slow) Methods using session(ephemeral) keys for the following additional reasons.

• Limit available cipher text(under a fixed key) for cryptanalytic attack;

• Limit exposurewith respect to both time period and quantity of data, in theevent of (session) key compromise;

• Avoid long-term storageof a large number of distinct secret keys (in thecase where one terminal communicates with a large number of others), bycreating keys only when actually required;

• Create independence across communicationssessions or applications. Noreplay attacks.

How to establish session keys over insecure medium where adversary is listen-ing to everything?Can be done even without any public key!Randomizationto rescue (like inCSMA/CD of Ethernet).

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Diffie-Hellman KeyEstablishment Protocol

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Man-in-the-middle attack

• Authentication was missing!

• Can be solved if Kasparov and Anand know each other’s public key(Needham-Schroeder).

• Yes, but different attack possible.

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Needham-SchroederProtocol

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Attack by Lowe (1995)

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Why Are Security ProtocolsOften Wrong?

They aretrivial programs built from simple primitives,BUT, they are compli-cated by

• concurrency

• a hostile environment

– a bad user controls the network

– Concern: active attacks masquerading, replay, man-in-middle, etc.

• vague specifications

– we have to guess what is wanted

• Ill-defined concepts

Protocol flaws rather than cryptosystem weaknessesFormal Methodsneeded!

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Online Voting ProtocolsAre we ready for elections via Internet?

• George Bush(Nov 2000, dimpled chads)

• Pervez Musharaf(April 2002)

• Gujarat(Dec 12, 2002)

E-Voting Protocols Requirements

• No loss of votes already cast (reliability)

• No forging of votes (authentication)

• No modification of votes cast (integrity)

• No multiple voting

• No vote secrecy violation (privacy)

• No vulnerability to vote coercion

• No vulnerability to vote selling or trading protocols (voter is an adversary)

• No loss of ability to cast and accept more votes (availability, no denial ofservice)

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Other Desirable Propertiesmust not only be correct and secure, but also be seen to be so by skeptical (buteducated and honest) outsiders.

• Auditability:

Failure or procedural error can be detected and corrected, especially theloss of votes.

• Verifiability: Should be able to prove

– My vote was counted

– All boothes were counted

– The number of votes in each booth is the same as the number of peoplewho voted

– No one I know who is ineligible to vote did so

– No one voted twice

– ...

without violating anonymity, privacy etc.Zero Knowledge Proofs

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RFC 2196 Site SecurityHandbook

Guidelines for any organization joining Internet

1. Risk Assessment (Assets/Threats)

2. Security Policies

3. Security Architecture and Services

• Firewalls, VPN, Encryption, ...

• Authentication

• Confidentiality, Integrity

• Authorization and Access Control

• Backups

4. Usage Monitorig and Auditing

5. Intrusion/Attack Detection

6. Security Incident Handling

No silver bulletor one timefix!Eternal Vigilance is the price of libertyhttp://web.iitb.ac.in

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References• Books

– TCP/IP Illustratedby Richard Stevens, Vols 1-3, Addison-Wesley.

– Applied Cryptography - Protocols, Algorithms, and Source Code in Cby BruceSchneier, Jon Wiley & Sons, Inc. 1996

– Cryptography and Network Security: Principles and Practiceby William Stallings (2ndEdition), Prentice Hall Press; 1998.

– Practical Unix and Internet Security,Simson Garfinkel and Gene Spafford, O’Reillyand Associates, ISBN 1-56592-148-8.

• Web sites

– www.cerias.purdue.edu(Centre for Education and Research in Information Assuranceand Security)

– www.sans.org(System Administration, Audit, Network Security)

– cve.mitre.org(Common Vulnerabilities and Exposures)

– csrc.nist.gov(Computer Security Resources Clearinghouse)

– www.vtcif.telstra.com.au/info/security.html

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