Computer Security and Authentication CS 5352 Spring 06
Jan 03, 2016
Computer Security and Authentication
CS 5352
Spring 06
Software Engineering Institute
• Federally funded, sponsored by DoD• Operated by Carnegie Mellon University• About 400 employees• Wants a smooth transfer of new Software
Engineering Technology into practice• Technical theme:
– Move left– Reuse everything– Never make the same mistake twice
CERT Coordination Center• Overview
– Part of the SEI– Formed by DARPA, 1988, after the worm incident– About 100 employees– 3,784 vulnerability reports (2003)– 137,529 computer security incidents (2003)
• Purpose– Analyse trends in attacks, vulnerabilities, impact– Coordinate responses to security attacks– Methods to evaluate, improve, maintain security – Publish, disseminate good security practices
Survivability
• The ability of a system to fulfill its mission, in a timely manner, in the presence of attacks, accidents, and failures
Critical Need for Information Assurance Incidents Reported to the CERT/CC
21756
52658
82094
137529
98593734213425732412
0
20000
40000
60000
80000
100000
120000
140000
160000
1995 1996 1997 1998 1999 2000 2001 2002 2003
Critical Need for Information Assurance Vulnerabilities Reported to the CERT/CC
3780
5990
1090
2437
4129
3784
417262311345171
0
1000
2000
3000
4000
5000
6000
7000
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005
AdvancedIntrudersDiscover
Vulnerability
Crude ExploitTools Distributed
Novice IntrudersUse Crude
Exploit Tools
AutomatedScanning/ExploitTools Developed
Widespread Use of Automated Scanning/Exploit Tools
Intruders Begin Using New Types of Exploits
Critical Need for Indications and Warnings
Critical Need for Indications and Warnings
Critical Need for Better Engineering Methods
• Resistance, recognition, and response must be integrated into the system and application architecture
Network protocols
• Designed for Arpanet, over 20 years ago
• But still used nowadays, under a totally different environment
A Different Internet• Armies may cease to march
• Stock may lose a hundred points
• Businesses may be bankrupted
• Individuals may lose their social identity
• Threats not from novice teenagers, but purposeful military, political, and criminal organizations
Why Should You Be Concerned
Personal data
Credit information
Medical information
Purchasing history
Corporate information
Political information
Societal infrastructure
Computer Vulnerability (2001)Out-of-the-box Linux PC hooked to Internet, not announced:[30 seconds] First service probes/scans detected[1 hour] First compromise attempts detected[12 hours] PC fully compromised:
– Administrative access obtained– Event logging selectively disabled– System software modified to suit intruder– Attack software installed– PC actively probing for new hosts to intrude
• Clear the disk and try again!
Motivations to Violate Security
• Ego
• Curiosity
• Greed
• Revenge
• Competition
• Political/Ideological
People and Computer Crime
• Most damage not due to attacks“Oops!”“What was that?”
• No clear profile of computer criminal
• Law and ethics may be unclear
Types of Attackers
• Script Kiddies
• Old-line hackers
• Disgruntled Employees
• Organized Crime
• Corporate Espionage
• Foreign Espionage
• Terrorists
Buffer overflow
• The most important avenue for vulnerabilities
• Good programming practice: always verify that the input you receive from uncontrolled source conforms to expected format
Buffer overflow example
rlogin programmain(argc,argv) int argc; char *argv[];{… char term[1024];...(void)strcpy(term, (p = getenv(“TERM”)) ? p: “network”);…}
Authentication
• Four classic ways to authenticate:1. something you know (passwords)
2. something you have (smartcard)
3. something you are (fingerprint)
4. something you do (usage signature)
• None of these is perfect
Identity theft
• Fastest rising crime in the US
• FBI won’t help unless losses above $100,000.
• Someone can steal an identity with just a social security number!!!
Passwords• Account - person using the system• Username - Identity of account (public)
– limited characters, alphanumeric & special characters– typically related to real name of user (not always), certain
names reserved – unique on system– fixed at account creation
• Passwords – Verification of identity (private)– Less limited length and characters– Fixed until changed– Non-unique passwords – (both users have bad password)
• Many Multi-user Operating Systems have same scheme
Password Security
• Password security depends on ONLY you knowing the password– Secure selection– Secure handling – Secure storage
Password Storage
• “trapdoor encrypted”– scrambled in a way that cannot be unscrambled– scrambling folds password over itself - lost bits– different users with same password won’t have
same scrambled password– login scrambles entered password and compares
against stored scrambled password– original concept: since only scrambled passwords
are available, storage is secure (FALSE!)
• longpre:br1eXN8N3pyAB
Password Attacks
• Easy to Hard– Given password– Grab password– Generate password– Guess password
Given Password• Look It Up
– Default passwords– Posted passwords
• Ask for It (Social Engineering)– As colleague– As friend– As administrator / authority– As clueless & needy
• Countermeasures– Education– Other authentication
Grab Password (locally)• Physical proximity
– Shoulder surfing– Countermeasures
• Education• Exercises• One-time passwords
• Program access– Trojan Horse– Perverted program– Countermeasures
• Integrity checks• Other authentication
Other Network Attacks• Tapping
– Method depends on network medium
– Countermeasures: • Encryption
• Physical protection & inspection
• Van Eck Radiation– Current through wire: Radio waves
– Receiver tunes in on hosts/network
– Countermeasures:• Encryption
• Distance
• Emission Control
Generate Password• Use a dictionary• Requires: Scrambled password,
Encryption method & Large dictionary• Password Cracking
– Natural language words and slang– Backwards / Forwards / Punctuation and Numbers
inserted– Program: 27,000 passwords in approx 3 seconds
(Pentium II/133)
• Countermeasures– Preventive strike (BEWARE)– Password rules– Other authentication
Guess Password• Use knowledge of user
– System information– Personal information– Occupation information
• Often combined with dictionary attack
• Countermeasures– Password rules– Other authentication
Password Changing• When?
– Forced or voluntary– Regularly or event driven
• Considerations– Increase security?
• Fix a stolen password problem• However, stolen passwords are often used quickly• False sense of security
– Too frequent password changes encourage• weak passwords • written down passwords
Passwords on Many Machines
• One or Many?– Ease of memorization vs. likelihood of writing – Options:
• Secure stored passwords
• Network authentication method
• Algorithm for varying passwords
• Seldom used passwords in encrypted file
Something You Have• Convert logical security to physical security
– One-time pad– Strip card / smart card– Dongle– Challenge-Response calculator
• Problems: Cost & token issuing/handling
• Advantages: Physical presence; hard to hack
Smart cards for identification• Hard to duplicate
• If weak protocol and a lot at stake, fakes WILL appear
• Use of zero-knowledge algorithms– Guarantee valid user but preserves privacy
• Attacks on smart cards– Power supply– Chemical stripping– Emissions
Something You Are• Biometrics: Measure physical characteristic
– Face geometry
– Hand geometry
– Fingerprint
– Voiceprint
– Retinal Scan
– Signature
• Advantages: Physical presence, not easily lost• Disadvantages: Cost, Security, Variation,
Handicaps, Success ratio