104/19/23 1
Instructor: Suprakash Datta (datta[at]cse.yorku.ca) ext 77875
Lectures: Tues (CB 122), 7–10 PM
Office hours: Wed 3-5 pm (CSEB 3043), or by appointment.
Textbooks: 1. "Management of Information Security", M. E. Whitman, H. J.
Mattord, Nelson Education / CENGAGE Learning, 2011, 3rd Edition 2. "Guide to Computer Forensics and Investigations", B. Nelson, A. Phillips, F. Enfinger, C. Steuart, Nelson Education / CENGAGE
Learning, 2010, 4th Edition.
CSE 4482: Computer Security Management: Assessment and Forensics
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Managing Firewalls
• Any firewall device must have its own configuration– Regulates its actions– Regardless of firewall implementation
• Policy regarding firewall use– Should be articulated before made operable
• Configuring firewall rule sets can be difficult– Each firewall rule must be carefully crafted,
placed into the list in the proper sequence, debugged, and tested
Management of Information Security, 3rd ed.
3
Managing Firewalls (cont’d.)
• Configuring firewall rule sets (cont’d.)– Proper sequence: perform most resource-
intensive actions after the most restrictive ones• Reduces the number of packets that undergo
intense scrutiny
• Firewalls deal strictly with defined patterns of measured observation– Are prone to programming errors, flaws in rule
sets, and other inherent vulnerabilities
Management of Information Security, 3rd ed.
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Managing Firewalls (cont’d.)
• Firewalls are designed to function within limits of hardware capacity– Can only respond to patterns of events that
happen in an expected and reasonably simultaneous sequence
Management of Information Security, 3rd ed.
5
Managing Firewalls (cont’d.)
• Firewall best practices– All traffic from the trusted network allowed out– The firewall is never accessible directly from
the public network– Simple Mail Transport Protocol (SMTP) data is
allowed to pass through the firewall• Should be routed to a SMTP gateway
– All Internet Control Message Protocol (ICMP) data should be denied
Management of Information Security, 3rd ed.
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Managing Firewalls (cont’d.)
• Firewall best practices (cont’d.)– Telnet (terminal emulation) access to all
internal servers from the public networks should be blocked
– When Web services are offered outside the firewall
• HTTP traffic should be handled by some form of proxy access or DMZ architecture
Management of Information Security, 3rd ed.
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Next: dealing with intrusions
• Intrusion detection and prevention
• Intrusion: attacker attempts to gain entry or disrupt normal operation
• Examples: password cracking, unauthorized data access, unauthorized software installation, unauthorized configuration changes, denial of service attacks
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Typical intrusion steps
• Initial reconnaissance (IP addrs, names, platforms…)
• Network probes: port scanning, ping
• Breaking in: gaining access to systems
• Take over the network: install rootkits,..
• Launch main attack: steal data, modify content, denial of service attacks,…
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Intrusion detection
A possible scenario (http://flylib.com/books/4/213/1/html/2/images/fig04_13.jpg)
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Intrusion Detection and Prevention Systems
• The term intrusion detection/prevention system (IDPS) can be used to describe current anti-intrusion technologies
• Can detect an intrusion
• Can also prevent that intrusion from successfully attacking the organization by means of an active response
Management of Information Security, 3rd ed.
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Intrusion Detection and Prevention Systems (cont’d.)
• IDPSs work like burglar alarms– Administrators can choose the alarm level– Can be configured to notify administrators via
e-mail and numerical or text paging
• Like firewall systems, IDPSs require complex configurations to provide the level of detection and response desired
• Active solutions!
Management of Information Security, 3rd ed.
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• The newer IDPS technologies– Different from older IDS technologies
• IDPS technologies can respond to a detected threat by attempting to prevent it from succeeding
– Types of response techniques:• The IDPS stops the attack itself• The IDPS changes the security environment• The IDPS changes the attack’s content
Management of Information Security, 3rd ed.
Intrusion Detection and Prevention Systems (cont’d.)
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IDPSs are either • host based to protect server or host
information assets• network based to protect network
information assets, or
IDPS detection methods • Signature based • Statistical anomaly based
Management of Information Security, 3rd ed.
Intrusion Detection and Prevention Systems (cont’d.)
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Intrusion Detection and Prevention Systems (cont’d.)
Management of Information Security, 3rd ed.
Figure 10-9 Intrusion detection and prevention systems
Source: Course Technology/Cengage Learning
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Host-based IDPS
• Resides on a particular computer or server and monitors activity only on that system
• Benchmark and monitor the status of key system files and detect when intruder creates, modifies, or deletes files
• Most HIDPSs work on the principle of configuration or change management
• Advantage over NIDPS: can usually be installed so that it can access information encrypted when traveling over network
From Principles of Information Security, Fourth Edition
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Host-Based IDPS (contd.)
• Configures and classifies various categories of systems and data files
• HIDPSs provide only a few general levels of alert notification
• Unless the HIDPS is very precisely configured, benign actions can generate a large volume of false alarms
• HIDPSs can monitor multiple computers simultaneously
Management of Information Security, 3rd ed.
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Advantages of HIDPSs
• Can detect local events on host systems and detect attacks that may elude a network-based IDPS
• Functions on host system, where encrypted traffic will have been decrypted and is available for processing
• Not affected by use of switched network protocols
• Can detect inconsistencies in how applications and systems programs were used by examining records stored in audit logs
From Principles of Information Security, Fourth Edition
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Disadvantages of HIDPSs
• Pose more management issues • Vulnerable both to direct attacks and attacks
against host operating system • Does not detect multi-host scanning, nor
scanning of non-host network devices • Susceptible to some denial-of-service attacks• Can use large amounts of disk space• Can inflict a performance overhead on its
host systems
From Principles of Information Security, Fourth Edition
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Network-Based IDPS
• Resides on computer or appliance connected to segment of an organization’s network; looks for signs of attacks
• Installed at specific place in the network where it can watch traffic going into and out of particular network segment
• Monitor network traffic– When a predefined condition occurs, notifies
the appropriate administrator
Management of Information Security, 3rd ed.
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Network-Based IDPS - contd
• Looks for patterns of network traffic
• Match known and unknown attack strategies against their knowledge base to determine whether an attack has occurred
• Yield many more false-positive readings than host-based IDPSs
Management of Information Security, 3rd ed.
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Advantages of NIDPSs
• Good network design and placement of NIDPS can enable organization to use a few devices to monitor large network
• NIDPSs are usually passive and can be deployed into existing networks with little disruption to normal network operations
• NIDPSs not usually susceptible to direct attack and may not be detectable by attackers
From Principles of Information Security, Fourth Edition
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Disadvantages of NIDPSs
• Can become overwhelmed by network volume and fail to recognize attacks
• Require access to all traffic to be monitored
• Cannot analyze encrypted packets• Cannot reliably ascertain if attack was
successful or not• Some forms of attack are not easily
discerned by NIDPSs, specifically those involving fragmented packets
From Principles of Information Security, Fourth Edition
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Signature-Based IDPS
• Examines data traffic for something that matches the preconfigured, predetermined attack pattern signatures– Also called knowledge-based IDPS– The signatures must be continually updated as
new attack strategies emerge– A weakness of this method:
• If attacks are slow and methodical, they may slip undetected through the IDPS, as their actions may not match a signature that includes factors based on duration of the events
Management of Information Security, 3rd ed.
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Statistical Anomaly-Based IDPS
• Also called behavior-based IDPS • First collects data from normal traffic and
establishes a baseline– Then periodically samples network activity, based on
statistical methods, and compares the samples to the baseline
– When activity falls outside the baseline parameters (clipping level), The IDPS notifies the administrator
Management of Information Security, 3rd ed.
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Statistical Anomaly-Based IDPS-2
Advantages:
• Able to detect new types of attacks, because it looks for abnormal activity of any type
• IDPS can detect new types of attacks
Disadvantages
• Requires much more overhead and processing capacity than signature-based
• May generate many false positives
Management of Information Security, 3rd ed.
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Selecting IDPS Approaches and Products
• Technical and policy considerations– What is your systems environment?– What are your security goals and
objectives?– What is your existing security policy?
• Organizational requirements and constraints– What are requirements that are levied from
outside the organization?– What are your organization’s resource
constraints?
Principles of Information Security, Fourth Edition
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Selecting IDPS Approaches and Products - contd
• IDPSs product features and quality– Is the product sufficiently scalable for your
environment? – How has the product been tested? – What is the user level of expertise targeted
by the product? – Is the product designed to evolve as the
organization grows?– What are the support provisions for the
product?
Principles of Information Security, Fourth Edition
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IDPS: Strengths
• IDPSs perform the following functions well:– Monitoring and analysis of system events and user
behaviors– Testing security states of system configurations– Baselining security state of system and tracking
changes– Recognizing system event patterns matching
known attacks– Recognizing activity patterns that vary from normal
activity
Principles of Information Security, Fourth Edition 28
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IDPS: Strengths - contd
• IDPSs perform the following functions well: (cont’d.)– Managing OS audit and logging mechanisms and
data they generate– Alerting appropriate staff when attacks are
detected– Measuring enforcement of security policies
encoded in analysis engine– Providing default information security policies– Allowing non-security experts to perform important
security monitoring functions
Principles of Information Security, Fourth Edition 29
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IDPSs: LimitationsIDPSs cannot perform the following functions:• Compensating for weak/missing security
mechanisms in protection infrastructure • Instantaneously detecting, reporting,
responding to attack when there is heavy network or processing load
• Detecting new attacks or variants of existing attacks
• Effectively responding to attacks by sophisticated attackers
• Investigating attacks without human intervention
Principles of Information Security, Fourth Edition
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IDPSs: Limitations (contd.)
IDPSs cannot perform the following functions (cont’d.):
• Resisting attacks intended to defeat or circumvent them
• Compensating for problems with fidelity of data sources
• Dealing effectively with switched networks
Principles of Information Security, Fourth Edition
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Deployment and Implementation of an IDPS
An IDPS can be implemented as• Centralized: all IDPS control functions are
implemented and managed in a central location
• Fully distributed: all control functions are applied at the physical location of each IDPS component
• Partially distributed: combines the two; while individual agents can still analyze and respond to local threats, they report to a hierarchical central facility to enable organization to detect widespread attacks
Principles of Information Security, Fourth Edition 32
33Principles of Information Security, Fourth Edition
Figure 7-4 Centralized IDPS Control13
34Principles of Information Security, Fourth Edition
Figure 7-5 Fully Distributed IDPS Control14
35Principles of Information Security, Fourth Edition
Figure 7-6 Partially Distributed IDPS Control15
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Deployment and Implementation of an IDPS (cont’d.)
• IDPS deployment– Like decision regarding control strategies, decision
about where to locate elements of intrusion detection systems can be art in itself
– Planners must select deployment strategy that is based on careful analysis of organization’s information security requirements but, at the same time, causes minimal impact
– NIDPS and HIDPS can be used in tandem to cover both individual systems that connect to an organization’s networks and networks themselves
Principles of Information Security, Fourth Edition
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Deploying network-based IDPSs
• Location 1: Behind each external firewall, in the network DMZ
• Location 2: Outside an external firewall
• Location 3: On major network backbones
• Location 4: On critical subnets
Principles of Information Security, Fourth Edition
NIST recommends four locations for NIDPS sensors
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Deploying host-based IDPSs
• Proper implementation of HIDPSs can be a painstaking and time-consuming task
• Deployment begins with implementing most critical systems first
• Installation continues until either all systems are installed or the organization reaches planned degree of coverage it is willing to live with
Principles of Information Security, Fourth Edition
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Measuring IDPS Effectiveness
• IDPSs are evaluated using four dominant metrics: thresholds, blacklists and whitelists, alert settings, and code viewing and editing
• Evaluation of IDPS might read: at 100 Mb/s, IDS was able to detect 97% of directed attacks
• Since developing this collection can be tedious, most IDPS vendors provide testing mechanisms that verify systems are performing as expected
Principles of Information Security, Fourth Edition
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Measuring IDPS Effectiveness - 2
• Some of these testing processes will enable the administrator to:– Record and retransmit packets from real
virus or worm scan– Record and retransmit packets from a real
virus or worm scan with incomplete TCP/IP session connections (missing SYN packets)
– Conduct a real virus or worm scan against an invulnerable system
Principles of Information Security, Fourth Edition
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Managing IDPS
• If there is no response to an alert, then an alarm does no good
• IDPSs must be configured to differentiate between routine circumstances and low, moderate, or severe threats
• A properly configured IDPS can translate a security alert into different types of notifications– A poorly configured IDPS may yield only noise
Management of Information Security, 3rd ed.
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Managing IDPS – contd.
• Most IDPSs monitor systems using agents– Software that resides on a system and reports
back to a management server
• Consolidated enterprise manager– Software that allows the security professional
to collect data from multiple host- and network-based IDPSs and look for patterns across systems and subnetworks
• Collecting responses from all IDPSs • Used to identify cross-system probes and intrusions
Management of Information Security, 3rd ed.
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Wireless Networking Protection
• Most organizations that make use of wireless networks use an implementation based on the IEEE 802.11 protocol
• The size of a wireless network’s footprint– Depends on the amount of power the
transmitter/receiver wireless access points (WAP) emit
– Sufficient power must exist to ensure quality connections within the intended area
• But not allow those outside the footprint to connect
Management of Information Security, 3rd ed.
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Wireless Networking Protection - 2
• War driving– Moving through a geographic area or building,
actively scanning for open or unsecured WAPs
• Common encryption protocols used to secure wireless networks– Wired Equivalent Privacy (WEP) – Wi-Fi Protected Access (WPA)
Management of Information Security, 3rd ed.
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Wired Equivalent Privacy (WEP)
• Provides a basic level of security to prevent unauthorized access or eavesdropping
• Does not protect users from observing each others’ data
• Has several fundamental cryptological flaws– Resulting in vulnerabilities that can be
exploited, which led to replacement by WPA
Management of Information Security, 3rd ed.
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Wi-Fi Protected Access (WPA)
• WPA is an industry standard– Created by the Wi-Fi Alliance
• Some compatibility issues with older WAPs
• IEEE 802.11i – Has been implemented in products such as
WPA2 • WPA2 has newer, more robust security protocols
based on the Advanced Encryption Standard
– WPA /WPA 2 provide increased capabilities for authentication, encryption, and throughput
Management of Information Security, 3rd ed.
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Wi-Max
• Wi-Max (WirelessMAN)– An improvement on the technology developed
for cellular telephones and modems – Developed as part of the IEEE 802.16
standard– A certification mark that stands for Worldwide
Interoperability for Microwave Access
Management of Information Security, 3rd ed.
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Bluetooth
• A de facto industry standard for short range (approx 30 ft) wireless communications between devices
• The Bluetooth wireless communications link can be exploited by anyone within range– Unless suitable security controls are implemented
• In discoverable mode devices can easily be accessed– Even in nondiscoverable mode, the device is
susceptible to access by other devices that have connected with it in the past
Management of Information Security, 3rd ed.
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Bluetooth (cont’d.)
• Does not authenticate connections– It does implement some degree of security
when devices access certain services like dial-up accounts and local-area file transfers
• To secure Bluetooth enabled devices: – Turn off Bluetooth when you do not intend to
use it – Do not accept an incoming communications
pairing request unless you know who the requestor is
Management of Information Security, 3rd ed.
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Managing Wireless Connections
• One of the first management requirements is to regulate the size of the wireless network footprint– By adjusting the placement and strength of the
WAPs
• Select WPA or WPA2 over WEP
• Protect preshared keys
Management of Information Security, 3rd ed.
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Honeypots, Honeynets, and Padded Cell Systems
• Honeypots: decoy systems designed to lure potential attackers away from critical systems
• Honeypots are designed to:– Divert attacker from accessing critical systems– Collect information about attacker’s activity– Encourage attacker to stay on system long
enough for administrators to document event and, perhaps, respond
• Honeynets: collection of honeypots connecting several honey pot systems on a subnet
Principles of Information Security, Fourth Edition
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Honeypots, Honeynets, and Padded Cell Systems (contd.)
• Padded cell: honeypot that has been protected so it cannot be easily compromised
• In addition to attracting attackers with tempting data, a padded cell operates in tandem with a traditional IDPS
• When the IDPS detects attackers, it seamlessly transfers them to a special simulated environment where they can cause no harm—the nature of this host environment is what gives approach the name padded cell
Principles of Information Security, Fourth Edition
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Honeypots, Honeynets, and Padded Cell Systems (contd.)
Advantages• Attackers can be diverted to targets they
cannot damage• Administrators have time to decide how to
respond to attacker• Attackers’ actions can be easily and more
extensively monitored, and records can be used to refine threat models and improve system protections
• Honeypots may be effective at catching insiders who are snooping around a network
Principles of Information Security, Fourth Edition
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Honeypots, Honeynets, and Padded Cell Systems (cont’d.)
Disadvantages• Legal implications of using such devices are
not well defined• Honeypots and padded cells have not yet
been shown to be generally useful security technologies
• Expert attacker, once diverted into a decoy system, may become angry and launch a more hostile attack against an organization’s systems
• Administrators and security managers need a high level of expertise to use these systems
Principles of Information Security, Fourth Edition
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Trap and Trace Systems
• Use combination of techniques to detect an intrusion and trace it back to its source
• Trap usually consists of honeypot or padded cell and alarm
• Legal drawbacks to trap and trace– Enticement: process of attracting attention to
system by placing tantalizing bits of information in key locations
– Entrapment: action of luring an individual into committing a crime to get a conviction
– Enticement is legal and ethical, entrapment is not
Principles of Information Security, Fourth Edition
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Active Intrusion Prevention
• Some organizations implement active countermeasures to stop attacks
• One tool (LaBrea) takes up unused IP address space to pretend to be a computer and allow attackers to complete a connection request, but then holds connection open
Principles of Information Security, Fourth Edition 56
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Scanning and Analysis Tools
• Used to find vulnerabilities in systems– Holes in security components, and other
unsecured aspects of the network
• Conscientious administrators frequently browse for new vulnerabilities, recent conquests, and favorite assault techniques
• Security administrators may use attacker’s tools to examine their own defenses and search out areas of vulnerability
Management of Information Security, 3rd ed.
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Scanning and Analysis Tools (contd.)
Scanning tools: Collect the information that an attacker needs
• Footprinting– The organized research of the Internet
addresses owned by a target organization
• Fingerprinting – The systematic examination of all of the
organization’s network addresses– Yields useful information about attack targets
Management of Information Security, 3rd ed.
59Principles of Information Security, Fourth Edition
Figure 7-9 Sam Spade
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Scanning and Analysis Tools
• Port mappers
• Network mappers
• Firewall analysis
• OS detection tools
• Vulnerability scanners
• Packet sniffers
• Wireless sniffers
• Password crackers
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Port Scanners
• A port is a network channel or connection point in a data communications system
• Port scanning utilities (port scanners) – Identify computers that are active on a
network, as well as their active ports and services, the functions and roles fulfilled by the machines, and other useful information
Management of Information Security, 3rd ed.
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Management of Information Security, 3rd ed.
Table10-5 Commonly used port numbers
Source: Course Technology/Cengage Learning
Port Scanners (cont’d.)
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Port Scanners (contd.)
• Well-known ports– Those from 0 through 1023– Registered ports are those from 1024 through
49151– Dynamic and private ports are those from
49152 through 65535
• Open ports must be secured– Can be used to send commands to a
computer, gain access to a server, and exert control over a networking device
Management of Information Security, 3rd ed.
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Network mappers
• Mostly use ICMP ping
• Most port scanners can be used as network mappers, e.g. Nmap, LanState
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Firewall Analysis• Several tools automate remote discovery of
firewall rules and assist the administrator in analyzing them
• Administrators who feel wary of using the same tools that attackers use should remember: – It is intent of user that will dictate how information
gathered will be used– In order to defend a computer or network well, it is
necessary to understand ways it can be attacked
• A tool that can help close up an open or poorly configured firewall will help network defender minimize risk from attack
Principles of Information Security, Fourth Edition
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Firewall Analysis – contd.
``Firewalking’’ steps• Network discovery – apply traceroute to a
host inside network (finds TTL count to firewall)
• Scanning – TCP/UDP packets with TTL of 1-hop past firewall sent; if the firewall allows packets in, ICMP TTL Expired message will be sent by binding host
• E.g. Firewalk
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OS Detection Tools
• Detecting a target computer’s operating system (OS) is very valuable to an attacker
• There are many tools that use networking protocols to determine a remote computer’s OS, e.g. Nmap, Xprobe
• Strategies: passive fingerprinting, active fingerprinting
Principles of Information Security, Fourth Edition
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Active fingerprinting• Find out more about host from TCP/IP
characteristics• TCP FIN probing: TCP RFC specifies that a FIN packet
to an open port should be ignored. MS Windows responds with a RST packet
• TCP Initial Sequence Number: Some OS choose random values. Windows generates it from the system clock
• TCP Initial window size: Linux 2.4 5840 bytes, 2.2 32120 bytes
• IP ID sampling: MSWin uses a predictable sequence, Linux chooses random numbers.
• ICMP Error message quoting: Linux quotes more than required
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Passive fingerprinting
Information gathered through sniffing• TTL in IP packets: normally Linux TTL= 64, MS
Windows TTL = 128• Don’t fragment bit in IP header: most OS 1,
OpenBSD 0• Type of service field in IP header: normally 0,
some OS non-zero
Generally less useful. Dependent on traffic pattern
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OS detection countermeasures
• Modify responses to various network events/packets
• Morph, IP Scrubber: “scrubs” clean any outgoing packets of OS relates information
• IP personality (http://ippersonality.sourceforge.net)
(patch for Linux kernel)
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Vulnerability Scanners
• Capable of scanning networks for very detailed information
• Variants of port scanners
• Identify exposed user names and groups, show open network shares, and expose configuration problems and other server vulnerabilities
Management of Information Security, 3rd ed.
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Vulnerability Scanners - 2
• Nessus – freeware
• Used by over 75000 companies
• Different versions for Unix, Mac, Windows
• Detects open ports, mis-configurations (e.g. missing patches), default passwords, presence of viruses, back-door programs
Management of Information Security, 3rd ed.
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Packet Sniffers
• A network tool that collects and analyzes packets on a network– It can be used to eavesdrop on network traffic
• Connects directly to a local network from an internal location
• To use a packet sniffer legally, you must:– Be on a network that the organization owns– Be directly authorized by the network’s owners– Have the knowledge and consent of the users– Have a justifiable business reason for doing so
Management of Information Security, 3rd ed.
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Packet Sniffers - 2
• Any network card can be switched to “promiscuous” mode to sniff all LAN packets
• Simply tapping into the Internet is a violation of wiretapping laws
• Example: Wireshark
Management of Information Security, 3rd ed.
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Wireless Sniffers
• Wireless sniffing is much easier than wired sniffing
• Very difficult to detect – leaves no traceable evidence
• Example: NetStumbler
Management of Information Security, 3rd ed.
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Password Crackers
Most systems store encrypted passwords. • MS Windows typically uses C:\Windows\
System32\config folder• Cannot be accessed directly by users, BUT
can be accessed by installing LCP, pwdump or FGDUMP (require Admin privilege to install).
• Encryption algorithm known (NT LAN Manager in Win 7)
• Case sensitive (unlike older versions of MSWin), applies MD4
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Password Crackers – contd.
Attack types • Brute force – very slow• Dictionary attack – only common disctionary
words used• Precomputed dictionary attack – saves time
required for encryption• E.g. Cain and Able or “Cain” (some virus
scanners detect it as malware! Microsoft Security Essentials “Tool: This program has potentially unwanted behavior”)
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Managing Scanning and Analysis Tools
• The security manager must be able to see the organization’s systems and networks from the viewpoint of potential attackers– The security manager should develop a
program to periodically scan his or her own systems and networks for vulnerabilities with the same tools that a typical hacker might use
• Using in-house resources, contractors, or an outsourced service provider
Management of Information Security, 3rd ed.
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Managing Scanning and Analysis Tools (cont’d.)
• Drawbacks:– Tools do not have human-level capabilities– Most tools function by pattern recognition, so
they only handle known issues – Most tools are computer-based, so they are
prone to errors, flaws, and vulnerabilities of their own
– Tools are designed, configured, and operated by humans and are subject to human errors
Management of Information Security, 3rd ed.
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Managing Scanning and Analysis Tools (cont’d.)
• Drawbacks: (cont’d.)– Some governments, agencies, institutions, and
universities have established policies or laws that protect the individual user’s right to access content
– Tool usage and configuration must comply with an explicitly articulated policy, and the policy must provide for valid exceptions
Management of Information Security, 3rd ed.
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Other measures
• Content filters
• Cryptographic tools
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Content Filters
• Protect systems from misuse – And unintentional denial-of-service conditions
• A software program or a hardware/software appliance that allows administrators to restrict content that comes into a network
• Common application of a content filter– Restriction of access to Web sites with non-
business-related material, such as pornography, or restriction of spam e-mail
– Content filters ensure that employees are using network resources appropriately
Management of Information Security, 3rd ed.
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Using Cryptographic Controls
• Modem cryptosystems can generate unbreakable ciphertext– Possible only when the proper key
management infrastructure has been constructed and when the cryptosystems are operated and managed correctly
Management of Information Security, 3rd ed.
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Using Cryptographic Controls (cont’d.)
• Cryptographic controls can be used to support several aspects of the business: – Confidentiality and integrity of e-mail and its
attachments Authentication, confidentiality, integrity, and nonrepudiation of e-commerce transactions
– Authentication and confidentiality of remote access through VPN connections
– A higher standard of authentication when used to supplement access control systems
Management of Information Security, 3rd ed.
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Using Cryptographic Controls
• Secure Multipurpose Internet Mail Extensions (S/MIME) – Builds on Multipurpose Internet Mail Extensions
(MIME) encoding format• Adds encryption and authentication via digital signatures
based on public key cryptosystems
• Privacy Enhanced Mail (PEM)– Proposed by the Internet Engineering Task Force
(IETF) as a standard that will function with public key cryptosystems
– Uses 3DES symmetric key encryption and RSA for key exchanges and digital signatures
Management of Information Security, 3rd ed.
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• Pretty Good Privacy (PGP) – Developed by Phil Zimmerman – Uses the IDEA Cipher
• A 128-bit symmetric key block encryption algorithm with 64-bit blocks for message encoding
– Like PEM, it uses RSA for symmetric key exchange and to support digital signatures
Management of Information Security, 3rd ed.
Using Cryptographic Controls (cont’d.)
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Using Cryptographic Controls
• IP Security (IPSec)– The primary and dominant cryptographic authentication
and encryption product of the IETF’s IP Protocol Security Working Group
– Combines several different cryptosystems: • Diffie-Hellman key exchange for deriving key material between
peers on a public network• Public key cryptography for signing the Diffie-Hellman
exchanges to guarantee the identity of the two parties • Bulk encryption algorithms, such as DES, for encrypting the
data• Digital certificates signed by a certificate authority to act as
digital ID cards
Management of Information Security, 3rd ed.
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Using Cryptographic Controls (cont’d.)
• IPSec has two components: – The IP Security protocol
• Specifies the information to be added to an IP packet and indicates how to encrypt packet data
– The Internet Key Exchange, which uses asymmetric key exchange and negotiates the security associations
Management of Information Security, 3rd ed.
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Using Cryptographic Controls (cont’d.)
• IPSec works in two modes of operation:– Transport
• Only the IP data is encrypted, not the IP headers themselves
• Allows intermediate nodes to read the source and destination addresses
– Tunnel• The entire IP packet is encrypted and inserted as
the payload in another IP packet
– Often used to support a virtual private network
Management of Information Security, 3rd ed.
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Using Cryptographic Controls (cont’d.)
• Secure Electronic Transactions (SET)– Developed by MasterCard and VISA to provide
protection from electronic payment fraud– Encrypts credit card transfers with DES for
encryption and RSA for key exchange
• Secure Sockets Layer (SSL)– Developed by Netscape in 1994 to provide
security for e-commerce transactions– Uses RSA for key transfer
• On IDEA, DES, or 3DES for encrypted symmetric key-based data transfer
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• Secure Hypertext Transfer Protocol– Provides secure e-commerce transactions and
encrypted Web pages for secure data transfer over the Web, using different algorithms
• Secure Shell (SSH)– Provides security for remote access connections over
public networks by using tunneling, authentication services between a client and a server
– Used to secure replacement tools for terminal emulation, remote management, and file transfer applications
Management of Information Security, 3rd ed.
Using Cryptographic Controls
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• Cryptosystems provide enhanced and secure authentication– One approach is provided by Kerberos, which
uses symmetric key encryption to validate an individual user’s access to various network resources
• Keeps a database containing the private keys of clients and servers that are in the authentication domain that it supervises
Management of Information Security, 3rd ed.
Using Cryptographic Controls (cont’d.)
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• Cryptosystems provide enhanced and secure authentication (cont’d.)– Kerberos system knows these private keys and
can authenticate one network node (client or server) to another
– Kerberos also generates temporary session keys—that is, private keys given to the two parties in a conversation
Management of Information Security, 3rd ed.
Using Cryptographic Controls (cont’d.)
94
Managing Cryptographic Controls
• Don’t lose your keys• Know who you are communicating with• It may be illegal to use a specific encryption
technique when communicating to some nations
• Every cryptosystem has weaknesses• Give access only to those with a business
need• When placing trust into a certificate
authority, ask “Who watches the watchers?”
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Managing Cryptographic Controls (cont’d.)
• There is no security in obscurity• Security protocols and the cryptosystems
they use are installed and configured by humans– They are only as good as their installers
• Make sure that your organization’s use of cryptography is based on well-constructed policy and supported with sound management procedures
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Summary
• Introduction
• Access controls
• Firewalls
• Intrusion detection and prevention systems
• Wireless network protection
• Scanning and analysis tools
• Cryptography
Management of Information Security, 3rd ed.
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