Chapter 1. Introduction to Data Communications

Chapter 1. Introduction to Data Communications

Business Data Communications and Networking 8th Edition Jerry Fitzgerald and Alan Dennis John Wiley & Sons, Inc Prof. M. Ulema Manhattan College Computer Information Systems Copyright 2005 John Wiley & Sons, Inc 11 - 1 Chapter 11 Network Security Copyright 2005 John Wiley & Sons, Inc

11 - 2 Outline Introduction Risk assessment Controlling disruption, destruction and disaster Controlling unauthorized access Preventing, detecting, and correcting Unauthorized Access Best practice recommendations Copyright 2005 John Wiley & Sons, Inc 11 - 3 Introduction Security - always a major business concern Protection of physical assets with locks, barriers,

guards, etc Protection of information with passwords, coding Introduction of computers and Internet Redefined the nature of information security Laws and enforcement Slow to catch-up Now a federal crime in the U.S. (breaking into a computer) New laws against cyberborder crimes; difficult to enforce Copyright 2005 John Wiley & Sons, Inc 11 - 4 Computer Security Incidents Growing at a rate of 100% per year 1988: a virus shut down 10% of the computers on the

Internet Establishment of Computer Emergency Response Team (CERT) with US DoD support Number of Incidents Reported to CERT Copyright 2005 John Wiley & Sons, Inc 11 - 5 Financial Impact of Security 2003 Computer Security Institute/FBI Computer Crime and Security Survey 90% of the respondents reported security breaches in the last 12 months 75% reported a financial loss due to security breaches Average loss: $2 million

Worldwide total annual cost of security losses Exceeds $2 trillion Reason for the increase in security problems Availability of sophisticated tools to break into networks Copyright 2005 John Wiley & Sons, Inc 11 - 6 Why Networks Need Security Organizations becoming vulnerable Becoming increasingly dependent on computers, networks Becoming increasingly vulnerable to due widely available Internet access to its computers and networks Huge losses due to security breaches $2 M average loss + losses related to less consumer confidence as a result of publicity of breaches

Potential losses from disruption of applications (Bank of America estimates $50 M per day) Protecting consumer privacy Strong laws against unauthorized disclosures (California: $250 K for each such incident) Protecting organizations data and application sw Value of data and applications >> network cost Copyright 2005 John Wiley & Sons, Inc 11 - 7 Primary Goals in Providing Security Confidentiality Protection of data from unauthorized disclosures of customers and proprietary data Integrity

Assurance that data have not been altered or destroyed Availability Providing continuous operations of hardware and software so that parties involved can be assured of uninterrupted service Copyright 2005 John Wiley & Sons, Inc 11 - 8 Types of Security Threats Business continuity planning related threats Disruptions Loss or reduction in network service Could be minor or temporary (a circuit failure) Destructions of data Viruses destroying files, crash of hard disk Disasters (Natural or manmade disasters )

May destroy host computers or sections of network Unauthorized access Hackers gaining access to data files and resources Most unauthorized access incidents involve employees Results: Industrial spying; fraud by changing data, etc. Copyright 2005 John Wiley & Sons, Inc 11 - 9 Example of Some Threats Copyright 2005 John Wiley & Sons, Inc 11 - 10 Example of Some Threats (Cont.) Copyright 2005 John Wiley & Sons, Inc

11 - 11 Network Controls Mechanisms that reduce or eliminate the threats to network security Types of controls: Preventative controls Mitigate or stop a person from acting or an event from occurring (e.g., locks, passwords, backup circuits) Act as a deterrent by discouraging or retraining Detective controls Reveal or discover unwanted events (e.g., auditing) Documenting events for potential evidence Corrective controls Rectify an unwanted event or a trespass (e.g., reinitiating a network circuit) Copyright 2005 John Wiley & Sons, Inc

11 - 12 Network Controls (Cont.) Also require personnel designated to: Develop controls Ensure that controls are operating effectively Update or replace controls when necessary Need to be reviewed periodically Ensure that the control is still present (verification) Determine if the control is working as specified (testing) Copyright 2005 John Wiley & Sons, Inc 11 - 13 Risk Assessment A key step in developing a secure network

Assigns level of risks to various threats By comparing the nature of threats to the controls designed to reduce them Use a control spreadsheet List down network assets on the side List threats across the top List the controls that are currently in use to address each threat in the corresponding cells Copyright 2005 John Wiley & Sons, Inc 11 - 14 Sample Control Spreadsheet Threats Assets (with Priority) Disruption, Destruction, Disaster Fire

Flood Power Circuit Virus Loss Failure Unauthorized Access External Internal EavesIntruder Intruder drop (92) Mail Server (90) Web Server (90) DNS Server (50) Computers on 6th floor (50) 6th floor LAN circuits (80) Building A Backbone (70) Router in Building A (30) Network Software (100) Client Database (100) Financial Database (70) Network Technical staff Copyright 2005 John Wiley & Sons, Inc

11 - 15 Network Assets Identify the assets on the network Organizations data files (most important) Mission critical applications (also very important) Programs critical to survival of business Hardware, software components Important, but easily replaceable Evaluate assets based on their importance Value of an asset Its replacement cost Personnel time to replace the asset Lost revenue due to the absence of the asset e.g., lost sales because a web server is down Copyright 2005 John Wiley & Sons, Inc

11 - 16 Types of Assets Hardware Servers, such as mail servers, web servers, DNS servers, DHCP servers, and LAN file servers Client computers Devices such as hubs, switches, and routers Circuits Locally operated circuits such LANs and backbones Contracted circuits such as MAN and WAN circuits Internet access circuits Network Software

Server operating systems and system settings Applications software such as mail server and web server software Client Software Operating systems and system settings Application software such as word processors Organizational Data Databases with organizational records Mission critical applications For example, for an Internet bank, the Web site is mission critical

Copyright 2005 John Wiley & Sons, Inc 11 - 17 Security Threats Identify threats Any potentially adverse occurrence that can Harm or interrupt the systems using the network, or Cause a monetary loss to an organization Rank threats according to Their probability of occurrence Likely cost if the threat occurs Take the nature of business into account Example: Internet banking vs. a restaurant Banks web site: has a higher probability of attack and much bigger loss if happens Restaurant web site: much less likely and small loss

Copyright 2005 John Wiley & Sons, Inc 11 - 18 Likelihood and Costs of Threats >>>> Fig 11.5 goes here Copyright 2005 John Wiley & Sons, Inc 11 - 19 Common Security Threats Virus infection most likely event Unauthorized access By internal and external hackers High cost to recover (both in $ and publicity) Device failure (not necessarily by a malicious act)

Device theft, Natural Disaster Denial of Service attacks External attacks blocking access to the network Big picture messages: Viruses: most common threat with a fairly high cost Unauthorized access by employees: greater threat Copyright 2005 John Wiley & Sons, Inc 11 - 20 Identify and Document Controls Identify current in-place controls and list them in the cell for each asset and threat For each asset and the specific threat Describe each control that Prevents, Detects and/or Corrects that threat

Place each control and its role in a numeric list (without any ranking) Place the number in the cell (in the control spreadsheet) Each cell may have one or more controls Copyright 2005 John Wiley & Sons, Inc 11 - 21 Sample Control Spreadsheet Threats Assets (with Priority) Disruption, Destruction, Disaster Fire Flood Power Circuit Virus Loss Failure

Unauthorized Access External Internal EavesIntruder Intruder drop (92) Mail Server 1,2 1,3 4 5, 6 7, 8 9, 10, 11 9, 10

(90) Web Server 1,2 1,3 4 5, 6 7, 8 9, 10, 11 9, 10 (90) DNS Server 1,2

1,3 4 5, 6 7, 8 9, 10, 11 9, 10 1,2 1,3 7, 8

10, 11 10 (50) 6th floor LAN circuits 1,2 1,3 (80) Building A Backbone 1,2 1,3 1,2 1,3

7, 8 9 9 (50) Computers on 6th floor (70) Router in Building A 6 (30) Network Software 7, 8 (100) Client Database

7, 8 (100) Financial Database (70) Network Technical staff 1 9, 10, 11 9, 10 9, 10, 11 9, 10 9, 10, 11 9, 10

1 Copyright 2005 John Wiley & Sons, Inc 11 - 22 List of Controls 1. 2. 3. 4. 5. 6. 7. 8. Disaster Recovery Plan Halon fire system in server room. Sprinklers in rest of building Not on or below ground level

Uninterruptible Power Supply (UPS) on all major network servers Contract guarantees from inter-exchange carriers Extra backbone fiber cable laid in different conduits Virus checking software present on the network Extensive user training on viruses and reminders in monthly newsletter 9. Strong password software 10. Extensive user training on password security and reminders in monthly newsletter 11. Application Layer firewall Copyright 2005 John Wiley & Sons, Inc 11 - 23 Evaluate the Networks Security Evaluate adequacy of the controls and resulting degree of risk associated with each threat Establish priorities for dealing with threats to

network security Which threats to be addressed immediately? Assessment can be done by Network manager, or A team of experts (better approach, a.k.a., Delphi team) Chosen (3-9 people) for their in-depth knowledge about the network and environment being reviewed Includes key managers (important for implementing final results) Copyright 2005 John Wiley & Sons, Inc 11 - 24 Business Continuity Planning Make sure that organizations data and applications will continue to operate even in the face of disruption, destruction, or disaster

Continuity Plan includes Development of controls To prevent these events from having a major impact Disaster recovery plan To enable the organization to recover if a disaster occurs Copyright 2005 John Wiley & Sons, Inc 11 - 25 Specifics of Continuity Plan Preventing Disruption, Destruction, and Disaster Using Redundant Hardware Preventing Natural Disaster Preventing Theft Preventing Viruses Preventing Denial of Service

Detecting Disruption, Destruction, and Disaster Correcting Disruption, Destruction, and Disaster Disaster Recovery Plan Disaster Recovery Outsourcing Copyright 2005 John Wiley & Sons, Inc 11 - 26 Using Redundant Hardware A key principal in preventing disruption, destruction and disaster Examples of components that provide redundancy Uninterruptible power supplies (UPS) A separate battery powered power supply Can supply power for minutes or even hours Fault-tolerant servers (with redundant components) Disk mirroring A redundant second disk for every disk on the server Every data on primary disk is duplicated on mirror

Disk duplexing (redundant disk controllers) Can apply to other network components as well Circuits, routers, client computers, etc., Copyright 2005 John Wiley & Sons, Inc 11 - 27 Preventing Natural Disasters More difficult to do Since the entire site can be destroyed by a disaster Fundamental principle: Decentralize the network resources Store critical data in at least two separate locations (in different part of the country) Best solution Have a completely redundant network that duplicates

every network component, but in a different location Other steps Depend on the type of disaster to be prevented Flood: Locate key components away from rivers Fire: Install Halon fire suppression system Copyright 2005 John Wiley & Sons, Inc 11 - 28 Preventing Theft Security plan must include: An evaluation of ways to prevent equipment theft Procedures to execute the plan Equipment theft A big problem About $1 billion lost each year to theft of

computers and related equipment Attractive good second hand market Making the m valuable to steal Copyright 2005 John Wiley & Sons, Inc 11 - 29 Preventing Computer Viruses Viruses (Macro viruses) Attach themselves to other programs (documents) and spread when the programs are executed (the files are opened) Worms Special type of virus that spread itself without human intervention (copies itself from computer to computer) Anti-virus software packages Check disks and files to ensure that they are virus-free

Incoming e-mail messages Most common source of viruses Attachments to e-mails to be checked for viruses Use of filtering programs that clean incoming e-mail Copyright 2005 John Wiley & Sons, Inc 11 - 30 Preventing Denial of Service Attacks DoS attacks Network disrupted by a flood of messages (prevents messages from normal users) Flooding web servers, email servers Distributed DoS (DDoS) Places DDoS agents into many computers Controls them by DDoS handler Example: Issues instructions to computers to send

simultaneous messages to a target computer Difficult to prevent DoS and DDoS attacks Setup many servers around the world Use Intrusion Detection Systems Require ISPs to verify that all incoming messages have valid IP addresses Copyright 2005 John Wiley & Sons, Inc 11 - 31 Detecting Disruption, Destruction, Disaster Recognize major problems quickly Involves alerting network managers to problems for corrective actions Requires clear procedures describing how to report problems quickly

Detecting minor disruptions More difficult Bad spots on a drive remaining unnoticed until it is checked Requires ongoing monitoring Requires fault information be routinely logged Copyright 2005 John Wiley & Sons, Inc 11 - 32 Disaster Recovery Plans (DRPs) Identify clear responses to possible disasters Provide for partial or complete recovery of All data, Application software, Network components, and Physical facilities Includes backup and recovery controls Make backup copies of all data and SW routinely Encrypt them and store them offsite

Should include a documented and tested approach to recovery Include Disaster Recovery Drills Should address what to do in situations like If the main database is destroyed If the data center is destroyed, how long Copyright 2005 John Wiley & Sons, Inc 11 - 33 Elements of a DRP Names of responsible individuals Staff assignments and responsibilities List of priorities of fix-firsts Location of alternative facilities Recovery procedures for data communications facilities, servers and application systems

Actions to be taken under various contingencies Manual processes Updating and Testing procedures Safe storage of data, software and the disaster recovery plan itself Copyright 2005 John Wiley & Sons, Inc 11 - 34 Two-Level DRPs Level 1: Build enough capacity and have enough spare equipment To recover from a minor disaster (e.g., loss of a major server or portion of the network) Could be very expensive Level 2: Rely on professional disaster recovery firms

To provide second level support for major disasters Copyright 2005 John Wiley & Sons, Inc 11 - 35 Disaster Recovery Firms Offer a range of services Secure storage for backups A complete networked data center that clients can use in disasters Complete recovery of data and network within hours Expensive, used by large organizations May be worthwhile when millions of dollars of lost revenue may be at stake Copyright 2005 John Wiley & Sons, Inc

11 - 36 Controlling Unauthorized Access Types of intruders Casual intruders With Limited knowledge (trying doorknobs) Script kiddies: Novice attackers using hacking tools Security experts (hackers) Motivation: the thrill of the hunt; show off Crackers: hackers who cause damage Professional hackers (espionage, fraud, etc) Breaking into computers for specific purposes Organization employees With legitimate access to the network Gain access to information not authorized to use Copyright 2005 John Wiley & Sons, Inc 11 - 37

Preventing Unauthorized Access Requires a proactive approach that includes routinely testing the security systems Best rule for high security Do not keep extremely sensitive data online Store them in computers isolated from the network Security Policy Critical to controlling risk due to access Should define clearly Important assets to be safeguarded and Controls needed What employees should do Plan for routinely training employees and testing security controls in place Copyright 2005 John Wiley & Sons, Inc 11 - 38

Elements of a Security Policy Names of responsible individuals Incident reporting system and response team Risk assessment with priorities Controls on access points to prevent or deter unauthorized external access Controls within the network to ensure internal users cannot exceed their authorized access An acceptable use policy User training plan on security Testing and updating plans Copyright 2005 John Wiley & Sons, Inc 11 - 39 Aspects of Preventing Unauthorized Access Securing the Network Perimeter

Securing the Interior of the network Most ignored aspects candy security security without this aspect crunchy outside, soft and chewy inside Authenticating users To make sure only valid users are allowed into the network Copyright 2005 John Wiley & Sons, Inc 11 - 40 Securing Network Perimeter Basic access points into a network LANs inside the organization Dial-up access through a modem Internet (most attacks come in this way)

Basic elements in preventing access Physical Security Dial-in security Firewalls and Network Address Translation (NAT) Proxy servers Copyright 2005 John Wiley & Sons, Inc 11 - 41 Physical Security Means preventing outsiders from gaining access into offices, server rooms, equipment Secure both main and remote facilities Implement proper access controls to areas where network equipment is located Only authorized personnel to access Each network component to have its own level of physical security

Have locks on power switches and passwords to disable keyboard and screens Be careful about distributed backup and servers Good for continuity, but bad for unauthorized access More equipment and locations to secure Copyright 2005 John Wiley & Sons, Inc 11 - 42 Personnel Matters Also important to Provide proper security education Perform background checks Implement error and fraud controls Reduces the possibility of attackers posing as

employees Example: Become employed as janitor and use various listening devices/computers to access the network Areas vulnerable to this type of access: Network Cabling Network Devices Copyright 2005 John Wiley & Sons, Inc 11 - 43 Securing Network Cables Easiest targets for eavesdropping Often run long distances and usually not checked regularly Easier to tap into local cables Easier to identify individual circuits/channels Control physical access by employees or vendors

to connectors and cables Secure local cables behind walls and above ceilings Keep equipment room locked and alarm controlled Choose a cable type harder to tap Harder to tap into fiber optic cables Pressurized cables: generates alarms when cut Copyright 2005 John Wiley & Sons, Inc 11 - 44 Securing Network Devices Should be secured in locked wiring closets More vulnerable: LAN devices (controllers, hubs, bridges, routers, etc.,) A sniffer (LAN listening device) can be easily hooked up to these devices Use secure hubs: requires special code

before a new computers are connected Copyright 2005 John Wiley & Sons, Inc 11 - 45 Dial-in Security Routinely change modem numbers Use call-back modems & automatic number identification (ANI) Only users dialing in from authorized locations are granted access User dials-in and logs into his/her account Modem (at server) hangs-up and dials back users modems prespecified number ANI: allows the user to dial in from several prespecified locations Use one-time only passwords

For traveling employees who cant use call-back modems and ANI Copyright 2005 John Wiley & Sons, Inc 11 - 46 Firewalls Prevent intruders (by securing Internet connections) From making unauthorized access and denial of service attacks to your network Could be a router, purpose computer gateway, or special Examines packets organizations network Restricts access to that network

flowing into and out of the Placed on every connection that network has to Internet Main types of firewalls Packet level firewalls (a.k.a., packet filters) Application-level firewalls (a.k.a., application gateway) Copyright 2005 John Wiley & Sons, Inc 11 - 47 Packet Filters Examines the source and destination address of packets passing through Allows only packets that have acceptable addresses to pass Examines IP Addresses and TCP ports only Firewall is unaware of applications and what the

intruder is trying to do IP spoofing remains a problem Done by simply changing the source address of incoming packets from their real address to an address inside the organizations network Firewall will pass this packet Copyright 2005 John Wiley & Sons, Inc 11 - 48 Application-Level Firewalls Acts as an intermediate host computer (between outside clients and internal servers) Forces anyone to login to this firewall and allows access only to authorized applications (e.g., Web site access) Separates a private network from the rest of the Internet Hides individual computers on the network behind the firewall

Some prohibits external users downloading executable files Software modifications done via physical access Requires more processing power than packet filters which can impact network performance Because of the increased complexity of what they do Copyright 2005 John Wiley & Sons, Inc 11 - 49 Network Address Translation (NAT) Used, by most firewalls, to shield a private network from outside interference Translates between private addresses inside a network and public addresses outside the network Done transparently (unnoticed by external computers) Internal IP addresses remain hidden

Performed by NAT proxy servers Uses an address table to do translations Ex: a computer inside accesses a computer outside Change source IP address to its own address Change source port number to a unique number Used as an index to the original source IP address Performs reverse operations for response packets Copyright 2005 John Wiley & Sons, Inc 11 - 50 Using Illegal Addresses with NAT Used to provide additional security Assigns illegal IP addresses to devices inside the network Even if they are discovered, no packets (with these addresses) from Internet will be delivered (illegal IP

address) Example: Assigned by ICANN: 128.192.55.xx Assign to NAT proxy server: Assign to internal computers: 10.3.3.xx 10.x.x.x is reserved for private networks (never used on Internet) No problem with users: NAT proxy server Big problem with intruders !! Copyright 2005 John Wiley & Sons, Inc 11 - 51 Use of NAT Proxy Servers Becoming popular; replacing firewalls Slow down message transfer Require at least two separate DNS servers For use by external users on Internet For use by internal users (internal DNS server)

Use of combined, layered approach Use layers of NAT proxy servers, packet filters and application gateways Maintaining online resources (for public access) in a DMZ network between the internal networks and the Internet Copyright 2005 John Wiley & Sons, Inc 11 - 52 A Network Design Using Firewalls For initial screening - Permits web access - Denies FTP requests Copyright 2005 John Wiley & Sons, Inc 11 - 53

Securing the Interior Security Holes Trojan Horses Encryption Copyright 2005 John Wiley & Sons, Inc 11 - 54 Security Holes Made by flaws in network software that permit unintended access to the network A bug that permits unauthorized access Operating systems often contain security holes Details can be highly technical Once discovered, knowledge about the security hole quickly circulated on the Internet

A race can then begin between Hackers attempting to break into networks through the security hole and Security teams working to produce a patch to eliminate the security hole CERT: major clearing house for Internet related holes Copyright 2005 John Wiley & Sons, Inc 11 - 55 Other Security Holes Flawed policies adopted by vendors New computers come with preinstalled user accounts with well known passwords Managers forgetting to change these passwords American government's OS security levels Minimum level (C2): provided by most OSs

Medium Level (B2): provided by some Highest level (A1 and A2): provided by few Copyright 2005 John Wiley & Sons, Inc 11 - 56 OS Security: Windows vs. Linux Windows Originally written for one user one computer User with full control Applications making changes to critical parts of the system Advantages: More powerful applications (without needing user to understand internals feature rich, easy to use applications Disadvantages: Hostile applications taking over the system Linux

Multi-users with various access rights Few system administrators with full control Copyright 2005 John Wiley & Sons, Inc 11 - 57 Trojan Horses Remote access management consoles that enable users to access a computer and manage it from afar More often concealed in another software that is downloaded over Internet Common carriers: Music and video files shared on Internet sites Undetected by antivirus software Major Trojans Back Office: attacked Windows servers Gives the attacker the same right as the administrator Morphed into tools such as MoSucker and Optix Pro

Powerful and easy to use Copyright 2005 John Wiley & Sons, Inc 11 - 58 Optix Pro Trojan Menu >>>>Fig. 11.11 goes here Copyright 2005 John Wiley & Sons, Inc 11 - 59 Encryption One of the best ways to prevent unauthorized access (more formally, cryptography) Process of disguising info by mathematical rules Main components of encryption systems Plaintext: Unencrypted message

Encryption algorithm: Works like the locking mechanism to a safe Key: Works like the safes combination Cipher text: Produced from the plaintext message by the encryption function Decryption - the same process in reverse Doesnt always use the same key or algorithm. Plaintext results from decryption Copyright 2005 John Wiley & Sons, Inc 11 - 60 Encryption Techniques Symmetric (private key) encryption Uses the same algorithm and key to both encrypt and decrypt a message Most common

Asymmetric (public key) encryption Uses two different one way keys: a public key used to encrypt messages a private key used to decrypt them Digital signatures Based on a variation of public key encryption Copyright 2005 John Wiley & Sons, Inc 11 - 61 Symmetric Encryption Key must be distributed Vulnerable to interception (an important weakness) Key management a challenge Strength of encryption Length of the secret key Longer keys more difficult to crack (more

combinations to try) Not necessary to keep the algorithm secret How to break an encryption Brute force: try all possible combinations until the correct key is found Copyright 2005 John Wiley & Sons, Inc 11 - 62 Symmetric Encryption Techniques Data Encryption Standard (DES) Developed by the US government and IBM Standardized and maintained by the National Institute of Standards and Technology (NIST) A 56-bit version of DES: used commonly, but can be broken by brute force (in a day) Not recommended for data needing high security

Other symmetric encryption techniques Triple DES (3DES): DES three times, effectively giving it a 168 bit key Advanced Encryption Standard (AES), designed to replace DES; uses 128, 192 and 256 bit keys RC4: a 40 bit key, but can use up to 256 bits Copyright 2005 John Wiley & Sons, Inc 11 - 63 Regulation of Encryptions Considered a weapon by the U.S. government Regulated its export the same way the weapons are Present rule: Prohibits the export of encryption techniques with keys longer than 56 bit Exemptions: Canada, European Union; American companies with foreign offices

Focus of an ongoing policy debate between security agencies and the software industry Many non-American companies and researchers developing more powerful encryption software Copyright 2005 John Wiley & Sons, Inc 11 - 64 Asymmetric Encryption Also known as Public Key Encryption (PKE) Most popular form of PKE: RSA Named (1977) after the initials of its inventors: Rivest, Shamir, and Adelman Forms the basis of Public Key Infrastructure (PKI) Patent expired in 2000; Now many companies offer it Longer keys: 512 bits or 1,024 bits Greatly reduces the key management problem

Publicized Public keys (in a public directory) Never distributed Private keys (kept secret) No need to exchange keys Use the others public key to encrypt Use the private key to decrypt Copyright 2005 John Wiley & Sons, Inc 11 - 65 PKE Operations 1 2 B makes its public key widely available (say through the Internet) message sender

3 No security hole is created by distributing the public key, since Bs private key has never been distributed. message recipient Copyright 2005 John Wiley & Sons, Inc 11 - 66 Digital Signatures Provide secure and authenticated message transmission (enabled by PKE) Provides a proof identifying the sender Important for certain (legal) transactions Digital Signature:

Includes the name of the sender and other key contents (e.g., date, time, etc.,) Use of PKE in reverse (applied to Digital Signature part of the message only) Outgoing: Encrypted using the senders private key Incoming: Decrypted using the senders public key Providing evidence who the message originated from Copyright 2005 John Wiley & Sons, Inc 11 - 67 Transmission with Digital Signatures Digital Signature only Organization A Organization B

Copyright 2005 John Wiley & Sons, Inc 11 - 68 Public Key Infrastructure (PKI) Set of hardware, software, organizations, and policies to make PKE work on Internet Solves the problem with digital signatures How to verify that the person sending the message Elements of PKI Certificate Authority (CA) A trusted organization that can vouch for the authenticity of the person of organization Certificate A digital document verifying the identity of a digital signatures source Fingerprint A unique key issued by the CA for every message sent

by the user (for higher security certification) Copyright 2005 John Wiley & Sons, Inc 11 - 69 Process with Certificate Authority User registers with a CA (e.g., VeriSign) Must provide some proof of Identity Levels of certification: Examples: Simple confirmation of an email address Complete police style background check CA issues a digital certificate User attaches the certificate to transactions (email, web, etc) Receiver authenticates transaction with CAs public key Contact CA to ensure the certificate is not revoked or expired

Copyright 2005 John Wiley & Sons, Inc 11 - 70 Pretty Good Privacy (PGP) A PKE freeware package Often used to encrypt e-mail Users make their public keys available Example: Posting them on Web pages Anyone wishing to send an encrypted message to that person Copies the public key from the Web page into the PGP software Encrypts (via PGP software) and sends the message using that key Copyright 2005 John Wiley & Sons, Inc

11 - 71 Secure Sockets Layer (SSL) A protocol widely used on the Web HTTP, FTP, SMTP Operates between the application and transport SSL layers Operations of SSL TCP IP Negotiation for PKI Server Send its public key and encryption

used (e.g., RC4, DES) Data Link technique to be Physical Browser Generates a key for this encryption technique; and sends it to the server (by encrypting with servers public key) Communications Encrypted by using the key generated by browser Copyright 2005 John Wiley & Sons, Inc 11 - 72 IP Security Protocol (IPSec)

Another widely used encryption protocol Can be used with other application layer (not just for web applications) Operations of IPSec between A and B protocols HTTP, FTP, SMTP TCP, UDP A and B generate and exchange two random keysIPSec using Internet Key Exchange (IKE) IP Then combine these two numbers to create Data Link encryption key to be used between A and B

Physical Next, A and B negotiate the encryption technique to be used, such as DES or 3DES. A and B then begin transmitting data using either: Transport mode: only the IP payload is encrypted Tunnel mode: entire IP packet is encrypted (needs a new header for routing in Internet Copyright 2005 John Wiley & Sons, Inc 11 - 73 Authenticating Users Done to ensure that only the authorized users are permitted into network and into the specific resources inside the network Basis of user authentication

User profile User accounts Passwords Biometric Network authentication Copyright 2005 John Wiley & Sons, Inc 11 - 74 User Profile Assigned to each user account by the manager Determines the limits of what users have access to on a network Allowable log-in day and time of day Allowable physical locations Allowable number of incorrect log-in attempts Specifies access details such as

Data and network resources a user can access Type of access (e.g., read, write, create, delete) Copyright 2005 John Wiley & Sons, Inc 11 - 75 Forms of Access Password based Users gain access based on something they know Not very secure due to poor choice of passwords Card based Users gain access based on something they have Smart cards, ATM cards Typically used in conjunction with a password One-time passwords Users connected to network obtains a password via: A pager

A token system (a separate handheld device) A network provided number is entered to device which generates the password Time-based tokens (password changes every 60 s) Generated by a device synchronized with server Copyright 2005 John Wiley & Sons, Inc 11 - 76 Biometric based Forms of Access Users gain access based on something they are Finger, hand, or retina scanning by a biometric system Convenient; no need to remember passwords Used in high-security applications; expensive

Low cost versions becoming available Fingerprint scanners with less than $100 Copyright 2005 John Wiley & Sons, Inc 11 - 77 Managing User Access Create accounts and profiles when new personnel arrive Remove user accounts when someone leaves an organization Often forgotten, creating big security problems Many systems allows now to set an expiration dates to the accounts When expires, deleted automatically Assign separate profiles and passwords to users using several different computers Cumbersome for users and managers as well

Adopt network authentication Helps manage users automatically Copyright 2005 John Wiley & Sons, Inc 11 - 78 Network Authentication Also called central authentication, single sign on, directory services Requires user to login to an authentication server Checks id and password against a database Issues a certificate Certificate used for all transactions requiring authentications No need to enter passwords Eliminates passwords changing hands

Kerberos most commonly used authentication protocol Copyright 2005 John Wiley & Sons, Inc 11 - 79 Managing Users Screen and classify both users and data Based on need to know Review the effect of any security software Focus on restriction or control access to files, records, or data items Provide adequate user training on network security Use self-teaching manuals, newsletters, policy statements, and short courses May eliminate social engineering attacks

Launch a well publicized security campaign To deter potential intruders Copyright 2005 John Wiley & Sons, Inc 11 - 80 Detecting Unauthorized Access Intrusion Detection Systems (IDSs): Network-based IDSs Install IDS sensors on network circuits and monitor packets Reports intrusions to IDS Management Console Host-based IDSs Monitor all activity on the server as well as incoming server traffic Application-based IDSs Special form of host-based IDSs Monitor just one application, such as a Web server

Copyright 2005 John Wiley & Sons, Inc 11 - 81 Techniques Used by IDSs Misuse detection Compares monitored activities with signatures of known attacks If an attack is recognized the IDS issues an alert and discards the packet Challenge: keep database current Anomaly detection Operates in stable computing environments Looks for major deviations from the normal parameters of network operation e.g., a large number of failed logins When detected, an alert is issued, packets discarded Problem: false alarms (valid traffic different from normal)

Copyright 2005 John Wiley & Sons, Inc 11 - 82 Use of IDSs with Firewalls Copyright 2005 John Wiley & Sons, Inc 11 - 83 Correcting Unauthorized Access Must have a clear plan to respond to breaches Have an emergency response team (CERT for Internet) Steps to take once intrusion detected: Identify where the security breach occurred and how it happened Helps to prevents other doing it the same way May report the problem to police

Use Computer Forensics area techniques Use of computer analysis techniques to gather evidence for trials Entrapments Use of honey pots Divert attackers to a fake server (with interesting, but fake data used as bait) Monitor access to this server; use it as a proof Copyright 2005 John Wiley & Sons, Inc 11 - 84 Best Practice Recommendations Start with a clear disaster recovery plan and solid security policies Train individuals on data recovery and social engineering Use routinely antivirus software, firewalls, physical security, intrusion detection, and encryption

>>>> Fig 11.15 goes here Copyright 2005 John Wiley & Sons, Inc 11 - 85 Personnel Security Recommendations >>>Fig 11.16 goes here Copyright 2005 John Wiley & Sons, Inc 11 - 86 Recommendations (Cont.) Use of strong centralized desktop management Prohibits individual users to change settings Use regular reimaging of computers to prevent Trojans and viruses

Install most recent security patches Prohibit al external software downloads Use continuous content filtering Scan all incoming packets Encrypt all server files and communications Enforce, vigorously, all written security policies Treat violations as capital offense Copyright 2005 John Wiley & Sons, Inc 11 - 87 Implications for Management Security - fastest growing area in networking Cost of security expected to increase More and sophisticated security tools to encounter ever increasing attacks Network becoming mission critical

More and skilled staff providing security Expect tougher laws and better enforcement Security to become a major factor to consider in choosing software and equipment More secure OSs, more secure application software, etc. Copyright 2005 John Wiley & Sons, Inc 11 - 88 Copyright 2005 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permissions Department, John Wiley & Sons, Inc. The purchaser may make

back-up copies for his/her own use only and not for distribution or resale. The Publisher assumes no responsibility for errors, omissions, or damages caused by the use of these programs or from the use of the information herein. Copyright 2005 John Wiley & Sons, Inc 11 - 89

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    'recognis[ing] commonalities and differences, creat[ing] connections with others and cultivat[ing] mutual respect' (ACARA, 2010) 'an openness to the world and a recognition of our deep interconnectedness to others […] students reflect on their own perspective, culture and identities, and then...
  • Python - NCU

    Python - NCU

    * * The whitewashing attack is made feasible by the availability of low cost identities or cheap pseudonyms. KaZaA: 由Niklas Zennström, Janus Friis, 和Priit Kasesalu 所開發(他們後來也開發了skype以及joost) 提供更好的匿名機制,可擴充性,以及容錯。 Mojo nation is a publishing and content-sharing network.
  • Chapter 26: Part 1 - Weebly

    Chapter 26: Part 1 - Weebly

    Chapter 26: Part 1. The Great West and the Agricultural Revolution ... Sioux blocking Bozeman trail killed and mutilated Fetterman's troops and civilians . Led to increased tension ... SD gold rush. Sitting Bull led Sioux, Arapaho, and Cheyenne to...


    - campus secretary will notify you when able to order. Receiving - notify campus secretary (quantities received) - large shipments to be prearranged with warehouse if necessary - turn in invoices and packing slips to Accts Pay. Purchasing Deadlines -...
  • Honeywell Solutions to Avioncs Manadates

    Honeywell Solutions to Avioncs Manadates

    Hong Kong (CAD): ADS-B Out for FL 290 to FL410 DO-260 or DO-260A Equipage by 12-DEC-2013. Limited to HKG-Registered aircraft operating on PBN Routes L6642 and M771 in HKG FIR. ADS-B Out for FL 290 to FL410 DO-260 or DO-260A...
  • Trigonometry/Pre-Calculus


    Converting decimal degrees to minutes and seconds. 4.2 Unit Circle 4.4 All Students Take Calculus 4.4 Evaluating Trig Functions of Any Angle Given and , find and . tan (-) and cos (+) = QIV Draw angle from origin to...