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Electronic Commerce
Tenth Edition
Chapter 10
Electronic Commerce Security
Learning Objectives
In this chapter, you will learn:
• What security risks arise in online business and how
to manage them
• How to create a security policy
• How to implement security on Web client computers
• How to implement security in the communication
channels between computers
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Learning Objectives (cont’d.)
• How to implement security on Web server
computers
• What organizations promote computer, network, and
Internet security
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Online Security Issues Overview
• Early Internet days
– Most popular use: electronic mail
• Today’s higher stakes
– Electronic mail, shopping, all types of financial
transactions
• Common worry of Web shoppers
– Stolen credit card as it transmits over the Internet
– More likely to be stolen from computer where stored
• Chapter topic: security in the context of electronic
commerce
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Origins of Security on Interconnected
Computer Systems
• Data security measures taken by Roman Empire
– Coded information to prevent enemies from reading
secret war and defense plans
• Modern electronic security techniques
– Defense Department wartime use
• “Orange Book”: rules for mandatory access control
• Business computers
– Initially adopted military’s security methods
• Today’s computing
– Requires comprehensive computer security plans
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Computer Security and Risk
Management
• Computer security
– Asset protection from unauthorized access, use,
alteration, and destruction
• Physical security
– Includes tangible protection devices
• Alarms, guards, fireproof doors, security fences, safes
or vaults, and bombproof buildings
• Logical security
– Asset protection using nonphysical means
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Computer Security and Risk
Management (cont’d.)
• Threat
– Any act or object posing danger to computer assets
• Countermeasure
– Procedure (physical or logical)
• Recognizes, reduces, and eliminates threat
– Extent and expense of countermeasures
• Vary depending on asset importance
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Computer Security and Risk
Management (cont’d.)
• Risk management model
– Four general organizational actions
• Impact (cost) and probability of physical threat
– Also applicable for protecting Internet and electronic
commerce assets from physical and electronic threats
• Electronic threat examples:
– Impostors, eavesdroppers, thieves
• Eavesdropper (person or device)
– Listen in on and copy Internet transmissions
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© Cengage Learning 2013
FIGURE 10-1 Risk management model
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Computer Security and Risk
Management (cont’d.)
• Crackers or hackers (people)
– Write programs; manipulate technologies
• Obtain unauthorized access to computers and
networks
• White hat hacker and black hat hacker
– Distinction between good hackers and bad hackers
• Good security scheme implementation
– Identify risks
– Determine how to protect threatened assets
– Calculate costs to protect assets
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Elements of Computer Security
• Secrecy
– Protecting against unauthorized data disclosure
– Ensuring data source authenticity
• Integrity
– Preventing unauthorized data modification
– Man-in-the-middle exploit
• E-mail message intercepted; contents changed before
forwarded to original destination
• Necessity
– Preventing data delays or denials (removal)
– Delaying message or completely destroying it
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Establishing a Security Policy
• Security policy
– Assets to protect and why, protection responsibility,
acceptable and unacceptable behaviors
– Physical security, network security, access
authorizations, virus protection, disaster recovery
• Military policy: stresses separation of multiple levels
of security
• Corporate information classifications
– Public
– Company confidential
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Establishing a Security Policy (cont’d.)
• Steps to create security policy
–
–
–
–
–
Determine assets to protect from threats
Determine access to various system parts
Identify resources to protect assets
Develop written security policy
Commit resources
• Comprehensive security plan goals
– Protect privacy, integrity, availability; authentication
– Selected to satisfy Figure 10-2 requirements
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© Cengage Learning 2013
FIGURE 10-2 Requirements for secure electronic commerce
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Establishing a Security Policy (cont’d.)
• Security policies information sources
– WindowSecurity.com site
– Information Security Policy World site
• Absolute security: difficult to achieve
– Create barriers deterring intentional violators
– Reduce impact of natural disasters and terrorist acts
• Integrated security
– Having all security measures work together
• Prevents unauthorized disclosure, destruction,
modification of assets
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Establishing a Security Policy (cont’d.)
• Security policy points
– Authentication: Who is trying to access site?
– Access control: Who is allowed to log on to and
access site?
– Secrecy: Who is permitted to view selected
information?
– Data integrity: Who is allowed to change data?
– Audit: Who or what causes specific events to occur,
and when?
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Security for Client Computers
• Client computers
– Must be protected from threats
• Threats
– Originate in software and downloaded data
– Malevolent server site masquerades as legitimate
Web site
• Chapter topics organized to follow the
transaction-processing flow
– Beginning with consumer
– Ending with Web server at electronic commerce site
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Cookies and Web Bugs
• Internet connection between Web clients and
servers
– Stateless connection
• Each information transmission is independent
• No continuous connection (open session) maintained
between any client and server
• Cookies
– Small text files Web servers place on Web client
– Identify returning visitors
– Allow continuing open session
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Cookies and Web Bugs (cont’d.)
• Time duration cookie categories
– Session cookies: exist until client connection ends
– Persistent cookies: remain indefinitely
– Electronic commerce sites use both
• Cookie sources
– First-party cookies
• Web server site places them on client computer
– Third-party cookies
• Different Web site places them on client computer
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Cookies and Web Bugs (cont’d.)
• Disable cookies entirely
– Complete cookie protection
– Problem
• Useful cookies blocked (along with others)
• Full site resources not available
• Web browser cookie management functions
– Refuse only third-party cookies
– Review each cookie before accepted
– Provided by most Web browsers
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FIGURE 10-3 Mozilla Firefox dialog box for managing stored cookies
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Cookies and Web Bugs (cont’d.)
• Web bug
– Tiny graphic that third-party Web site places on
another site’s Web page
– Purpose
• Provide a way for a third-party site to place cookie on
visitor’s computer
• Internet advertising community:
– Calls Web bugs “clear GIFs” or “1-by-1 GIFs”
• Graphics created in GIF format
• Color value of “transparent,” small as 1 pixel by 1 pixel
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Active Content
• Active content
– Programs embedded transparently in Web pages
– Cause action to occur
– E-commerce example
• Place items into shopping cart; compute tax and costs
• Advantages
– Extends HTML functionality
– Moves data processing chores to client computer
• Disadvantages
– Can damage client computer
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Active Content (cont’d.)
• Cookies, Java applets, JavaScript, VBScript,
ActiveX controls, graphics, Web browser plug-ins,
e-mail attachments
• Scripting languages: provide executable script
– Examples: JavaScript and VBScript
• Applet: small application program
– Typically runs within Web browser
• Some browsers include tools limiting applets’ actions
• Active content modules
– Embedded in Web pages (invisible)
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FIGURE 10-4 Advanced JavaScript settings in Mozilla Firefox
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Active Content (cont’d.)
• Crackers: embed malicious active content
• Trojan horse
– Program hidden inside another program or Web page
• Masking true purpose
– May result in secrecy and integrity violations
• Zombie (Trojan horse)
– Secretly takes over another computer
– Launches attacks on other computers
• Botnet (robotic network, zombie farm)
– All controlled computers act as an attacking unit
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Java Applets
• Java programming language
– Developed by Sun Microsystems
– Widespread use in Web pages: active content
• Java: platform-independent programming language
–
–
–
–
Provides Web page active content
Server sends applets with client-requested pages
Most cases: operation visible to visitor
Possibility: functions not noticed by visitor
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Java Applets (cont’d.)
• Advantages
– Adds functionality to business application’s
functionality; relieves server-side programs
• Disadvantage
– Possible security violations (Trojan horse, zombie)
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Java Applets (cont’d.)
• Java sandbox
– Confines Java applet actions to set of rules defined
by security model
– Rules apply to all untrusted Java applets
• Not established as secure
– Java applets running within sandbox constraint
• Does not allow full client system access
• Prevents secrecy (disclosure) and integrity (deletion or
modification) violations
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JavaScript
• JavaScript
–
–
–
–
Scripting language developed by Netscape
Enables Web page designers to build active content
Based loosely on Sun’s Java programming language
Can be used for attacks
• Cannot commence execution on its own
• User must start ill-intentioned JavaScript program
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ActiveX Controls
• ActiveX control
– Objects containing programs and properties Web
designers place on Web pages
• Component construction
– Many different programming languages
• Common: C++ and Visual Basic
• Run on Windows operating systems computers
• Executed on client computer like any other program
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ActiveX Controls (cont’d.)
• Comprehensive ActiveX controls list
– ActiveX page at Download.com
• Security danger
– Execute like other client computer programs
– Have access to full system resources
• Cause secrecy, integrity, and necessity violations
– Actions cannot be halted once started
• Web browsers
– Provide notice of Active-X download or install
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FIGURE 10-5 ActiveX control download warning dialog box in Internet Explorer
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Graphics and Plug-Ins
• Graphics, browser plug-ins, and e-mail attachments
can harbor executable content
• Graphic: embedded code can harm client computer
• Browser plug-ins (programs)
– Enhance browser capabilities
– Popular plug-ins: Adobe Flash Player, Apple’s
QuickTime Player, Microsoft Silverlight,
RealNetworks’ RealPlayer
– Can pose security threats
• 1999 RealPlayer plug-in
• Plug-ins executing commands buried within media
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Viruses, Worms, and Antivirus
Software
• Programs display e-mail attachments by
automatically executing associated programs
– Macro viruses within attached files can cause damage
• Virus: software
– Attaches itself to another program
– Causes damage when host program activated
• Worm: virus
– Replicates itself on computers it infects
– Spreads quickly through the Internet
• Macro virus
– Small program (macro) embedded in file
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Viruses, Worms, and Antivirus
Software (cont’d.)
• ILOVEYOU virus (“love bug”)
–
–
–
–
Spread with amazing speed
Infected computers and clogged e-mail systems
Replicated itself explosively through Outlook e-mail
Caused other harm
• 2001 Code Red and Nimda: virus-worm
combinations
– Multivector virus: entered computer system in
several different ways (vectors)
• 2002 and 2003: new virus-worm combinations
– Example: Bugbear
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Viruses, Worms, and Antivirus
Software (cont’d.)
• Antivirus software
– Detects viruses and worms
– Either deletes or isolates them on client computer
• 2005 and 2006 Zotob
– New breed of Trojan horse-worm combination
• 2007: Storm virus
• 2008 and continuing into 2009: Conflicker
• 2009 and 2010: URLzone and Clampi
– New viruses designed specifically to hijack users’
online banking sessions
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Viruses, Worms, and Antivirus
Software (cont’d.)
• 2010: new Trojan horse-worm combination attack
– Spread through a computer operating system
– Designed to target industrial equipment
• German industrial giant Siemens’ control systems
• 2011: Zeus and SpyEye combined
– Targeted bank account information
– Not visible in Microsoft Windows Task Manager
– Intercept credit card or online banking data entered in
Web browser
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FIGURE 10-6 Major viruses, worms, and Trojan horses
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FIGURE 10-6 Major viruses, worms, and Trojan horses (continued)
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FIGURE 10-6 Major viruses, worms, and Trojan horses (continued)
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FIGURE 10-6 Major viruses, worms, and Trojan horses (continued)
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FIGURE 10-6 Major viruses, worms, and Trojan horses (continued)
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FIGURE 10-6 Major viruses, worms, and Trojan horses (continued)
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Viruses, Worms, and Antivirus
Software (cont’d.)
• Companies that track viruses, sell antivirus software,
provide virus descriptions on Web sites
– Symantec (Symantec Security Response)
– McAfee (McAfee Virus Information)
• Data files must be updated regularly
– Recognize and eliminate newest viruses
• Some Web e-mail systems:
– Provide and update antivirus software
• Used to scan attachments before downloading
– Example: Yahoo! Mail
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Digital Certificates
• Digital certificate (digital ID)
– E-mail message attachment or program embedded in
Web page
– Verifies sender or Web site
– Contains a means to send encrypted message
– Signed message or code
• Provides proof of holder identified by the certificate
– Used for online transactions
• Electronic commerce, electronic mail, and electronic
funds transfers
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© Cengage Learning 2013
FIGURE 10-7 Delmar Cengage Learning’s digital certificate information displayed
in Firefox browser
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Digital Certificates (cont’d.)
• Digital certificate for software:
– Assurance software was created by specific company
– Does not attest to quality of software
• Certification authority (CA)
– Issues digital certificates to organizations, individuals
• Digital certificates cannot be forged easily
• Six main elements: owner’s identifying information,
owner’s public key, dates certificate is valid, serial
number, issuer name, issuer digital signature
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Digital Certificates (cont’d.)
• Key
– Number: usually long binary number
• Used with encryption algorithm
• “Lock” message characters being protected
– Longer keys provide better protection
• Identification requirements vary
– Driver’s license, notarized form, fingerprints
• Companies offering CA services
– Thawte, VeriSign, Comodo, DigiCert, Entrust,
GeoTrust, RapidSSL.com
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Digital Certificates (cont’d.)
• Secure Sockets Layer-Extended Validation
(SSL-EV) digital certificate
– Issued after more extensive verification confirmed
• Annual fees
– $200 to more than $1500
• Digital certificates expire after period of time
– Provides protection (users and businesses)
– Must submit credentials for reevaluation periodically
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FIGURE 10-8 Internet Explorer address window display for an SSL-EV Web site
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Steganography
• Steganography
– Hiding information within another piece of information
• Can be used for malicious purposes
• Hiding encrypted file within another file
– Casual observer cannot detect anything of
importance in container file
– Two-step process
• Encrypting file protects it from being read
• Steganography makes it invisible
• Al Qaeda used steganography to hide attack orders
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Physical Security for Clients
• Client computers
– Control important business functions
– Same physical security as early systems
• New physical security technologies
– Fingerprint readers (less than $100)
• Stronger protection than password approaches
• Biometric security device
– Identification using element of person’s biological
makeup
• Writing pads, eye scanners, palm reading scanners,
reading back of hand vein pattern
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Client Security for Mobile Devices
• Security measures
– Access password
– Remote wipe: clears all personal data
• Can be added as an app
• Capability through corporate e-mail synchronization
– Antivirus software
• Rogue apps: contain malware or collect information
and forward to perpetrators
– Apple App Store tests apps before authorizing sales
– Android Market does less extensive testing
– Users should not rush to install latest app
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Communication Channel Security
• Internet
– Not designed to be secure
– Designed to provide redundancy
• Remains unchanged from original insecure state
– Message traveling on the Internet
• Subject to secrecy, integrity, and necessity threats
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Secrecy Threats
• Secrecy
– Prevention of unauthorized information disclosure
– Technical issue
• Requiring sophisticated physical and logical
mechanisms
• Privacy
– Protection of individual rights to nondisclosure
– Legal matter
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Secrecy Threats (cont’d.)
• E-mail message
– Secrecy violations protected using encryption
• Protects outgoing messages
– Privacy issues address whether supervisors are
permitted to read employees’ messages randomly
• Electronic commerce threat
– Sensitive or personal information theft
– Sniffer programs
• Record information passing through computer or router
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Secrecy Threats (cont’d.)
• Electronic commerce threat (cont’d.)
– Backdoor: electronic holes
• Left open accidentally or intentionally
• Content exposed to secrecy threats
• Example: Cart32 shopping cart program backdoor
– Stolen corporate information
• Eavesdropper example
• Web users continually reveal information
– Secrecy breach
– Possible solution: anonymous Web surfing
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Integrity Threats
• Also known as active wiretapping
– Unauthorized party alters message information
stream
• Integrity violation example
– Cybervandalism
• Electronic defacing of Web site
• Masquerading (spoofing)
– Pretending to be someone else
– Fake Web site representing itself as original
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Integrity Threats (cont’d.)
• Domain name servers (DNSs)
– Internet computers maintaining directories
• Linking domain names to IP addresses
– Perpetrators use software security hole
• Substitute their Web site address in place of real one
• Spoofs Web site visitors
• Phishing expeditions
– Capture confidential customer information
– Common victims
• Online banking, payment system users
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Necessity Threats
• Also known as delay, denial, denial-of-service
(DoS) attack
– Disrupt or deny normal computer processing
– Intolerably slow-speed computer processing
• Renders service unusable or unattractive
• Distributed denial-of-service (DDoS) attack
– Launch simultaneous attack on a Web site via botnets
• DoS attacks
– Remove information altogether
– Delete transmission or file information
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Necessity Threats (cont’d.)
• Denial attack examples:
– Quicken accounting program diverted money to
perpetrator’s bank account
– High-profile electronic commerce company received
flood of data packets
• Overwhelmed sites’ servers
• Choked off legitimate customers’ access
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Threats to the Physical Security of
Internet Communications Channels
• Internet’s packet-based network design:
– Precludes it from being shut down
• By attack on single communications link
• Individual user’s Internet service can be interrupted
– Destruction of user’s Internet link
• Larger companies, organizations
– Use more than one link to main Internet backbone
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Threats to Wireless Networks
• Wireless Encryption Protocol (WEP)
– Rule set for encrypting transmissions from the
wireless devices to the wireless access points (WAPs)
• Wardrivers
– Attackers drive around in cars
– Search for accessible networks
• Warchalking
– Place chalk mark on building
• Identifies easily entered wireless network nearby
– Web sites include wireless access locations maps
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Threats to Wireless Networks (cont’d.)
• Preventing attacks by wardrivers
– Turn on WEP
– Change default login and password settings
• Example
– Best Buy wireless point-of-sale (POS)
• Failed to enable WEP
• Customer launched sniffer program
• Intercepted data from POS terminals
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Encryption Solutions
• Encryption: coding information using
mathematically based program, secret key
• Cryptography: science studying encryption
– Science of creating messages only sender and
receiver can read
• Steganography
– Makes text undetectable to naked eye
• Cryptography converts text to other visible text
– With no apparent meaning
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Encryption Solutions (cont’d.)
• Encryption algorithms
– Encryption program
• Transforms normal text (plain text) into cipher text
(unintelligible characters string)
– Encryption algorithm
• Logic behind encryption program
• Includes mathematics to do transformation
– Decryption program
• Encryption-reversing procedure: message is decoded
or decrypted
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Encryption Solutions (cont’d.)
• Encryption algorithms (cont’d.)
– National Security Agency controls dissemination
– U.S. government banned publication of details
• Illegal for U.S. companies to export
– Encryption algorithm property
• May know algorithm details
• Unable to decipher encrypted message without
knowing key encrypting the message
– Key type subdivides encryption into three functions
• Hash coding, asymmetric encryption, symmetric
encryption
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Encryption Solutions (cont’d.)
• Hash coding
– Process uses Hash algorithm
– Calculates number (hash value) from any length
message
– Unique message fingerprint
– Good hash algorithm design
• Probability of collision is extremely small (two different
messages resulting in same hash value)
– Determining message alteration during transit
• Mismatch between original hash value and receiver
computed value
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Encryption Solutions (cont’d.)
• Asymmetric encryption (public-key encryption)
– Encodes messages using two mathematically related
numeric keys
– Public key: one key freely distributed to public
• Encrypt messages using encryption algorithm
– Private key: second key belongs to key owner
• Kept secret
• Decrypt all messages received
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Encryption Solutions (cont’d.)
– Pretty Good Privacy (PGP)
– Software tools using different encryption algorithms
• Perform public key encryption
– Individuals download free versions
• PGP Corporation site, PGP International site
• Encrypt e-mail messages
– Sells business site licenses
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Encryption Solutions (cont’d.)
• Symmetric encryption (private-key encryption)
– Encodes message with one of several available
algorithms
• Single numeric key to encode and decode data
– Message receiver must know the key
– Very fast and efficient encoding and decoding
– Key must be guarded
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Encryption Solutions (cont’d.)
– Problems
• Difficult to distribute new keys to authorized parties
while maintaining security, control over keys
• Private keys do not work well in large environments
– Data Encryption Standard (DES)
• Encryption algorithms adopted by U.S. government
• Most widely used private-key encryption system
• Fast computers break messages encoded with smaller
keys
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Encryption Solutions (cont’d.)
– Triple Data Encryption Standard (Triple DES,
3DES)
• Stronger version of Data Encryption Standard
– Advanced Encryption Standard (AES)
• Alternative encryption standard
• Most government agencies use today
– Longer bit lengths increase difficulty of cracking keys
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Encryption Solutions (cont’d.)
• Comparing asymmetric and symmetric encryption
systems
– Advantages of public-key (asymmetric) systems
• Small combination of keys required
• No problem in key distribution
• Implementation of digital signatures possible
– Disadvantages of public-key systems
• Significantly slower than private-key systems
– Public-key systems: complement rather than replace
private-key systems
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© Cengage Learning 2013
FIGURE 10-9 Comparison of
(a) hash coding, (b) private-key,
and (c) public-key encryption
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Encryption Solutions (cont’d.)
– Web servers accommodate encryption algorithms
• Must communicate with variety of Web browsers
– Secure Sockets Layer (SSL)
• Goal: secures connections between two computers
– Secure Hypertext Transfer Protocol (S-HTTP)
• Goal: send individual messages securely
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Encryption Solutions (cont’d.)
• Secure sockets layer (SSL) protocol
– Provides security “handshake”
– Client and server exchange brief burst of messages
– All communication encoded
• Eavesdropper receives unintelligible information
– Secures many different communication types
• HTTP, FTP, Telnet
– HTTPS: protocol implementing SSL
• Precede URL with protocol name HTTPS
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Encryption Solutions (cont’d.)
– Encrypted transaction generates private session key
• Bit lengths vary (40-bit, 56-bit, 128-bit, 168-bit)
– Session key
• Used by encryption algorithm
• Creates cipher text from plain text during single secure
session
– Secrecy implemented using public-key and privatekey encryption
• Private-key encryption for nearly all communications
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© Cengage Learning 2013
FIGURE 10-10 Establishing an SSL session
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Encryption Solutions (cont’d.)
– After secure session established:
• Public-key encryption no longer used
• Message transmission protected by private-key
encryption
• Session key (private key) discarded when session ends
– Each new connection between client and secure
server requires entire process:
• Beginning with handshake
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Encryption Solutions (cont’d.)
• Secure HTTP (S-HTTP)
– Extension to HTTP providing security features
• Client and server authentication, spontaneous
encryption, request/response nonrepudiation
– Symmetric encryption for secret communications
– Public-key encryption to establish client/server
authentication
– Session negotiation: process between client and
server of proposing and accepting (or rejecting)
various transmission conditions
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Encryption Solutions (cont’d.)
– Establishing secure session
• SSL carries out client-server handshake exchange to
set up secure communication
• S-HTTP sets up security details with special packet
headers exchanged in S-HTTP
– Headers define security technique type
– Header exchanges state:
• Which specific algorithms that each side supports
• Whether client or server (or both) supports algorithm
• Whether security technique required, optional, refused
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Encryption Solutions (cont’d.)
– Secure envelope (complete package)
• Encapsulates message
• Provides secrecy, integrity, and client/server
authentication
• SSL has become:
– More generally accepted standard over S-HTTP
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Using a Hash Function to Create a
Message Digest
• Integrity violation
– Message altered while in transit
• Difficult and expensive to prevent
• Security techniques to detect
• Harm: unauthorized message changes undetected
• Apply two algorithms to eliminate fraud and abuse
– Hash algorithm
– Message digest
• Number summarizing encrypted information
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Converting a Message Digest into a
Digital Signature
• Hash functions: potential for fraud
– Solution: sender encrypts message digest using
private key
• Digital signature
– Encrypted message digest (message hash value)
• Digital signature provides:
– Integrity, nonrepudiation, and authentication
• Provide transaction secrecy
– Encrypt entire string (digital signature, message)
• Digital signatures: same legal status as traditional
signatures
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© Cengage Learning 2013
FIGURE 10-11 Sending and receiving a digitally signed message
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Security for Server Computers
• Server vulnerabilities
– Exploited by anyone determined to cause destruction
or acquire information illegally
• Entry points
– Web server and its software
– Any back-end programs containing data
• No system is completely safe
• Web server administrator
– Ensures security policies documented; considered in
every electronic commerce operation
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Web Server Threats
• Compromise of secrecy
– By allowing automatic directory listings
– Solution: turn off folder name display feature
• Sensitive file on Web server
– Holds Web server username-password pairs
– Solution: store authentication information in encrypted
form
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Web Server Threats (cont’d.)
• Passwords that users select
– Easily guessable
• Dictionary attack programs cycle through electronic
dictionary, trying every word as password
– Solutions
• User password requirements
• Use password assignment software to check user
password against dictionary
• Help creating very strong passwords:
– Gibson Research Corporation’s Ultra High Security
Password Generator
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© Cengage Learning 2013
FIGURE 10-12 Examples of passwords, from very weak to very strong
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Database Threats
• Usernames and passwords
– Stored in unencrypted table
– Database fails to enforce security altogether
• Relies on Web server to enforce security
• Unauthorized users
– Masquerade as legitimate database users
• Trojan horse programs hide within database system
– Reveal information
– Remove all access controls within database
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Other Programming Threats
• Java or C++ programs executed by server
– Passed to Web servers by client
– Reside on server
– Use a buffer
• Memory area set aside holding data read from file or
database
– Buffer overrun (buffer overflow) error
•
•
•
•
Programs filling buffers malfunction and overfill buffer
Excess data spilled outside designated buffer memory
Cause: error in program or intentional
1998 Internet worm
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Other Programming Threats (cont’d.)
• Insidious version of buffer overflow attack
– Writes instructions into critical memory locations
– Web server resumes execution by loading internal
registers with address of attacking program’s code
• Reducing potential buffer overflow damage
– Good programming practices
– Some hardware functionality
• Mail bomb attack
– Hundreds (thousands) send message to particular
address
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Threats to the Physical Security of Web
Servers
• Protecting Web servers
– Put computers in commerce service provider (CSP)
facility
• Very high-level physical security on CSP
– Maintain server content’s backup copies at remote
location
– Rely on service providers
• Offer managed services including Web server security
– Hire smaller, specialized security service providers
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Access Control and Authentication
• Controlling who and what has access to Web server
• Authentication
– Identity verification of entity requesting computer
access
• Server user authentication
– Server must successfully decrypt user’s digital
signature-contained certificate
– Server checks certificate timestamp
– Server uses callback system
• Certificates authenticate client computers and their
users
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Access Control and Authentication
(cont’d.)
• Usernames and passwords
– Provide some protection element
• Maintain usernames in plain text
– Encrypt passwords with one-way encryption algorithm
• Problem
– Site visitor may save username and password as a
cookie
• Might be stored in plain text
• Access control list (ACL)
– Restrict file access to selected users
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Firewalls
• Firewall
– Software, hardware-software combination
– Installed in a network to control packet traffic
• Placed at Internet entry point of network
– Defense between network and the Internet
• Between network and any other network
• Principles
– All traffic must pass through it
– Only authorized traffic allowed to pass
– Immune to penetration
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Firewalls (cont’d.)
•
•
•
•
Trusted: networks inside firewall
Untrusted: networks outside firewall
Filter permits selected messages though network
Separate corporate networks from one another
– Coarse need-to-know filter
• Firewalls segment corporate network into secure zones
• Large organizations with multiple sites
– Install firewall at each location
• All locations follow same security policy
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Firewalls (cont’d.)
• Should be stripped of unnecessary software
• Packet-filter firewalls
– Examine all data flowing back and forth between
trusted network (within firewall) and the Internet
• Gateway servers
– Filter traffic based on requested application
– Limit access to specific applications
• Telnet, FTP, HTTP
• Proxy server firewalls
– Communicate with the Internet on private network’s
behalf
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Firewalls (cont’d.)
• Perimeter expansion problem
– Computers outside traditional physical site boundary
• Servers under almost constant attack
– Install intrusion detection systems
• Monitor server login attempts
• Analyze for patterns indicating cracker attack
• Block further attempts originating from same IP
address
• Cloud computing: firewall products lagging behind
• Personal firewalls
– Software-only firewalls on individual client computers
– Gibson Research Shields Up! Web site
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Organizations that Promote Computer
Security
• Following the Internet Worm of 1988
– Organizations formed to share information
• About threats to computer systems
• Principle followed
– Sharing information about attacks and defenses for
attacks
• Helps everyone create better computer security
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CERT
• Computer Emergency Response Team
• Housed at Carnegie Mellon University
– Software Engineering Institute
• Maintains effective, quick communications
infrastructure among security experts
– Security incidents avoided, handled quickly
• Provides security risk information
• Posts security event alerts
• Primary authoritative source for viruses, worms, and
other types of attack information
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Other Organizations
• 1989: System Administrator, Audit, Network and
Security (SANS) Institute
– Education and research efforts
• Research reports, security alerts, and white papers
– SANS Internet Storm Center Web site
• Current information on location, intensity of computer
attacks worldwide
• CERIAS (Center for Education and Research in
Information Assurance and Security)
– Multidisciplinary information security research and
education
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Other Organizations (cont’d.)
• Center for Internet Security
– Not-for-profit cooperative organization
– Helps electronic commerce companies
• CSO Online
– Articles from CSO Magazine
– Computer security-related news items
• Infosecurity.com
– Articles about all types of online security issues
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Computer Forensics and Ethical
Hacking
• Computer forensics experts (ethical hackers)
– Computer sleuths hired to probe PCs
– Locate information usable in legal proceedings
– Job of breaking into client computers
• Computer forensics field
– Responsible for collection, preservation, and
computer-related evidence analysis
• Companies hire ethical hackers to test computer
security safeguards
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Summary
• Physical and logical computer security important in
electronic commerce
– Security policy can identify risks and countermeasures
to reduce risks
• Key security provisions
– Secrecy, integrity, available service
• Client threats and solutions
– Virus threats, active content threats, cookies
• Communication channels’ threats and solutions
– Encryption provides secrecy
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Summary (cont’d.)
• Web Server threats and solutions
– Threats from programs, backdoors
• Security organizations
– Share information about threats, defenses
• Computer forensics
– “Break into” computers searching for legal use data
– Assist in identifying security weaknesses
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