ITEC 275 Computer Networks – Switching, Routing, and

WANs

Week 8Robert D’Andrea

Some slides provide by Priscilla Oppenheimer and used with permission

Agenda• Learning Activities– Security– Threats and Risks– Security Policy– Security Mechanisms–Wireless Security– SNMP

Network Security DesignThe 12 Step Program

1. Identify network assets2. Analyze security risks3. Analyze security requirements and tradeoffs4. Develop a security plan5. Define a security policy6. Develop procedures for applying security

policies

The 12 Step Program (continued)7. Develop a technical implementation strategy8. Achieve buy-in from users, managers, and technical

staff9. Train users, managers, and technical staff10. Implement the technical strategy and security

procedures11. Test the security and update it if any problems are

found12. Maintain security

Network Assets

Network AssetsAn enterprise's assets may be broadly

divided into two categories: physical assets which include buildings, machinery, financial assets and infrastructure. Hardware, such as, routers, internetworking devices, cabling, and switches are all necessary devices needed to conduct a business.

Network AssetsNetwork Assets

The second category of assets, intangible assets which range from human capital and know-how to ideas, brands, designs and other intangible fruits of a company's creative and innovative capacity. Traditionally, physical assets have been responsible for the bulk of the value of a company, and were considered to be largely responsible for determining the competitiveness of an enterprise in the market place. In recent years, the situation has changed significantly.

Network Assets

Network AssetsIncreasingly, and largely as a result of

the information technologies revolution and the growth of the service economy, companies are realizing that intangible assets are often becoming more valuable than their physical assets.

Network AssetsNetwork Assets• Software(Operating systems, applications, and

data)Less Obvious Network Assets• Intellectual property is the collective wisdom

of your employees or customers is vast and waiting to be tapped. Bloomfire is a knowledge base built to capture, archive, and grow the knowledge that already exists within or about your organization.

Network AssetsNetwork AssetsBloomfire develops software that allows companies to share information on a web-based application platform. The software application, launched in 2012, allows users to create team communities where people can post questions and answers, and add or create new content. The content can be uploaded in the form of videos, photos or text documents. The social platform allows users to "follow", "share", and "like" other users' content; it also has screen-recording capabilities. The software aims to increase accessibility to information within a company. The application can be accessed from a device connected to the Internet, such as a PC, laptop, tablet computer, or smartphone.

Network Assets• Trade secrets is any confidential business

information which provides an enterprise a competitive edge may be considered a trade secret. Trade secrets encompass manufacturing or industrial secrets and commercial secrets. The unauthorized use of such information by persons other than the holder is regarded as an unfair practice and a violation of the trade secret.

• Company’s reputation the reputation of a business is essential to its survival. The trust and confidence of the consumer can have a direct and profound effect on a company's bottom ...

Network AssetsView:Designing Security for Microsoft Networkshttps://www.youtube.com/watch?v=THP9VdIDG98

Security Risks• Hacked network devices–Data can be intercepted, analyzed,

altered, or deleted–User passwords can be compromised–Device configurations can be changed

• Reconnaissance attacks (are used to initially gather information about a target network or system. At first glance, seem harmless).

• Denial-of-service (DoS) attacks are increasing

Security Tradeoffs• Tradeoffs must be made between security

goals and other goals:– Affordability– Usability– Performance– Availability–ManageabilityThe cost of protecting yourself against a threat should be less than the cost of recovering if the threat were to strike you.

A Security Plan

• High-level document that proposes what an organization is going to do to meet security requirements. This is a corporate level decision.

• Specifies time, people, and other resources that will be required to develop a security policy and achieve implementation of the policy

A Security Plan

• Should reference the network topology and include a list of network services that will be provided. The list should specify who provides the services, who has access to the services, how access is provided, and who administers the services.

A Security Policy

• Informs users, managers, and technical staff of their obligations for protecting technology and information assets. Normally, this is an agreement employees sign as a part of their tenure.

A Security Policy

• Per RFC 2196, “The Site Security Handbook,” a security policy is a– “Formal statement of the rules by which people

who are given access to an organization’s technology and information assets must abide.”

• The policy should address– Access, accountability, authentication, privacy,

and computer technology purchasing guidelines

Security Mechanisms

• Physical security ( Limited access toresources )

• Authentication (Who is requestingnetwork services)

• Authorization (Who can access networkresources)

• Accounting (Auditing – collecting data)• Data encryption (a process of scrambling

data to protect it’s integrity)

Security Mechanisms

• Packet filters (can be set up on routers, firewalls, and servers to accept or deny packets from

a particular address or service) • Firewalls (a device that enforces security policies at the boundary between two or more networks). Traditional,

are best suited for small businesses needs.

Security Mechanisms• Detect and prevent denial of service (DoS) attacks with TCP

Intercept, Context-Based Access Control (CBAC), and rate-limiting techniques

• Use Network-Based Application Recognition (NBAR) to detect and filter unwanted and malicious traffic

• Use router authentication to prevent spoofing and routing attacks• Activate basic Cisco IOS filtering features like standard,

extended, timed, lock-and-key, and reflexive ACLs to block various types of security threats and attacks, such as spoofing, DoS, Trojan horses, and worms

• Use black hole routing, policy routing, and Reverse Path Forwarding (RPF) to protect against spoofing attacks

Security Mechanisms• Apply stateful filtering of traffic with CBAC, including dynamic port

mapping• Use Authentication Proxy (AP) for user authentication• Perform address translation with NAT, PAT, load distribution, and other

methods• Implement stateful NAT (SNAT) for redundancy• Use Intrusion Detection System (IDS) to protect against basic types of

attacks• Obtain how-to instructions on basic logging and learn to easily interpret

results• Apply IPSec to provide secure connectivity for site-to-site and remote

access connections• Read about many, many more features of the IOS firewall for mastery of

router security

Security Mechanisms

The Cisco IOS firewall offers you the feature-rich functionality that you've come to expect from best-of-breed firewalls: address translation, authentication, encryption, stateful filtering, failover, URL content filtering, ACLs, NBAR, and many others. Cisco Router Firewall Security teaches you how to use the Cisco IOS firewall to enhance the security of your perimeter routers and, along the way, take advantage of the flexibility and scalability that is part of the Cisco IOS Software package.

Security Mechanisms

• Intrusion Detection Systems (IDS) (detects malicious events and notifies an administrator using email, paging, or logging of the occurrences).• Intrusion Prevention Systems (IPS) (blocks traffic by adding rules to a firewall or by being configured to inspect traffic as it enters a firewall).

Encryption for Confidentiality and Integrity

• Public/Private key encryption - Asymmetric key system- All devices use the public key to encrypt

data to be sent.- Receiving devices decrypt the data using a

private key• Digital signature

- Encrypt part of your document with a private key- Receiver decrypts document using your public key

Encryption for Confidentiality and Integrity

After encrypting your document with your private key, you can encrypt the document with another public key (IRS). The IRS decrypts the document twice.

Encryption for Confidentiality and Integrity

Encryption for Confidentiality and Integrity

Figure 8-1. Public/Private Key System for Ensuring Data Confidentiality

Figure 8-2. Public/Private Key System for Sending a Digital Signature

Modularizing Security DesignCisco supports reputation filtering and

global correlation services, so that an IPS can keep-up-to-date on global security trends and more accurately deny traffic from networks known to be currently associated with botnets, spam, and other malware.

Modularizing Security Design• Security defense in depth– Network security should be multilayered with

many different techniques used to protect the network.

Modularizing Security Design• Belt-and-suspenders approach– Don’t get caught with your pants down. Each

mechanism should have a backup mechanism.The belt and suspender ensure security of

the pants (system) staying up. Use a dedicated firewall to limit access to resources and a packet-filtering router that adds another line of defense ( multilayer of defense).

Modularizing Security Design

• Secure all components of a modular design:– Internet connections– Public servers and e-commerce servers– Remote access networks and VPNs– Network services and network management– Server farms– User services–Wireless networks

Securing Internet Connections• Physical security• Firewalls and packet filters• Audit logs, authentication, authorization• Well-defined exit and entry points• Routing protocols that support authenticationInternet routers should be backed up with additional filters to prevent DoS (Denial of Service) and other attacks. In turn, these filters should be backed up additional filters placed on firewall devices. Monitor Internet

Cisco SAFE• Cisco SAFE Security Reference Model addresses

security in every module of a modular network architecture.

Securing Public Servers

• Place servers in a DMZ that is protected via firewalls

• Run a firewall on the server itself• Enable DoS (denial of service) protection– Limit the number of connections per timeframe

• Use reliable operating systems with the latest security patches

• Maintain modularity– Front-end Web server doesn’t also run other services

Security Topologies

EnterpriseNetwork

DMZ

Web, File, DNS, Mail Servers

Internet

Security Topologies

Internet

Enterprise NetworkDMZ

Web, File, DNS, Mail Servers

Firewall

Securing Remote-Access and Virtual Private Networks (VPN)

• Physical security• Firewalls• Authentication, authorization, and auditing• Encryption• One-time passwords

Securing Remote-Access and Virtual Private Networks

• Security protocols– Remote users and routers should authenticate with

CHAP – Authentication, authorization, and accounting is

RADIUS. The database includes authentication and configuration information. Specifies types of services a user is permitted to implement (PPP, FTP, Telnet).

– IPsec is an IETF standard that provides confidentiality, data integrity, and authentication between participating peers at the IP layer, IPsec provides a secure path between remote users and a VPN concentrator, and between remote sites and a VPN site-to-site gateway.

Securing Remote-Access and Virtual Private Networks

Virtual Private Networkhttps://www.youtube.com/watch?v=q4P4BjjXghQ

IP Securityhttp://www.youtube.com/watch?v=taUdRQHfjMQ

Securing Network Services• Treat each network device (routers, switches, and

so on) as a high-value host and harden it against possible intrusions

• Require login IDs and passwords for accessing devices– Require extra authorization for risky configuration

commands• Use SSH (Secure Shell) rather than Telnet• Change the welcome banner to be less welcoming

Securing Network Services• Routing protocols should be selected that

support authentication, including RIPv2, OSPF, EIGRP, and BGP4.

• Static and default routes are good choices because they eliminate the need to accept routing updates.

• Execute minimal necessary services and establish trust in only authenticated partners.

Securing Server Farms• Deploy network and host IDSs to monitor server

subnets and individual servers• Configure filters that limit connectivity from the

server in case the server is compromised• Fix known security bugs in server operating

systems• Require authentication and authorization for

server access and management• Limit root password to a few people• Avoid guest accounts

Securing User Services• Specify which applications are allowed to

run on networked PCs in the security policy• Require personal firewalls and antivirus

software on networked PCs– Implement written procedures that specify how

the software is installed and kept current• Encourage users to log out when leaving

their desks• Consider using 802.1X port-based security

on switches

Securing Wireless Networks• Place wireless LANs (WLANs) in their own

subnet or VLAN– Simplifies addressing and makes it easier to

configure packet filters• Require all wireless (and wired) laptops to run

personal firewall and antivirus software• Disable beacons that broadcast the SSID, and

require MAC address authentication– Except in cases where the WLAN is used by visitors

Securing Wireless Networks• IEEE802.11 Specifies Two Forms of Authentication

- Open key the client is always authenticated. used for guest access.- Shared key authentication, a WEP (Wired

Equivalent Privacy) static key must be properly configured in both the client and the access point.Man-in-the-middle is another form of eavesdropping

WLAN Security Options• Wired Equivalent Privacy (WEP) vulnerable to passive

attacks and inductive key derivations. If the key is determined, it must be changed on the access point and every client.

• IEEE 802.11i• Wi-Fi Protected Access (WPA)• IEEE 802.1X Extensible Authentication Protocol (EAP)

– Lightweight EAP or LEAP (Cisco)– Protected EAP (PEAP)

• Virtual Private Networks (VPNs)• Any other acronyms we can think of?)• Service Set Identifier (SSID)

Wired Equivalent Privacy (WEP)

• Defined by IEEE 802.11• Users must possess the appropriate WEP key

that is also configured on the access point– 64 or 128-bit key (or passphrase)

• WEP encrypts the data using the RC4 stream cipher method

• Infamous for being crackeable

WEP Alternatives

• Vendor enhancements to WEP• Temporal Key Integrity Protocol (TKIP)– Every frame has a new and unique WEP key

• Advanced Encryption Standard (AES) • IEEE 802.11i (implemented as WEP2)• Wi-Fi Protected Access (WPA) from the

Wi-Fi Alliance

Extensible Authentication Protocol (EAP)

• With 802.1X and EAP, devices take on one of three roles:– The supplicant resides on the wireless LAN client– The authenticator resides on the access point - An authentication server resides on a RADIUS server EAP authenticates users. 802.11 authenticates device based (wireless LAN devices)

EAP (Continued)• An EAP supplicant on the client obtains credentials

from the user, which could be a user ID and password

• The credentials are passed by the authenticator to the server and a session key is developed

• Periodically the client must re-authenticate to maintain network connectivity

• Re-authentication generates a new, dynamic WEP key

Cisco’s Lightweight EAP (LEAP)• Standard EAP plus mutual authentication– The user and the access point must authenticate

• Used on Cisco and other vendors’ products• Mutual authentication means the client

authenticates the server and the server authenticates the client.

Other EAPs• EAP-Transport Layer Security (EAP-TLS) was developed by

Microsoft– Requires certificates for clients and servers.

• Protected EAP (PEAP) is supported by Cisco, Microsoft, and RSA Security– Uses a certificate for the client to authenticate the RADIUS

server– The server uses a username and password to authenticate

the client• EAP-MD5 has no key management features or dynamic key

generation– Uses challenge text like basic WEP authentication– Authentication is handled by RADIUS server

VPN Software on Wireless Clients• VPN is the safest way to do wireless networking for

corporations• Wireless client requires VPN software• Connects to VPN concentrator at HQ• Creates a tunnel for sending all traffic• VPN security provides:– User authentication– Strong encryption of data– Data integrity

Network Management• Helps an organization achieve availability,

performance, and security goals • Helps an organization measure how well

design goals are being met and adjust network parameters if they are not being met

• Facilitates scalability– Helps an organization analyze current network

behavior, apply upgrades appropriately, and troubleshoot any problems with upgrades

Network Management Design• Consider scalability, traffic patterns, data

formats, cost/benefit tradeoffs• Determine which resources should be

monitored• Determine metrics for measuring performance• Determine which and how much data to

collect

Proactive Network Management

• Plan to check the health of the network during normal operation, not just when there are problems

• Recognize potential problems as they develop

• Optimize performance• Plan upgrades appropriately

Network Management Processes According to the ISO

1. Fault management2. Configuration management3. Accounting management4. Performance management5. Security management

Fault Management• Detect, isolate, diagnose, and correct problems• Report status to end users and managers• Track trends related to problems

Configuration Management

• Keep track of network devices and their configurations

• Maintain an inventory of network assets• Log versions of operating systems and

applications

Accounting Management

• Keep track of network usage by departments or individuals

• Facilitate usage-based billing• Find users who use more resources than they

should

Performance Management

• Monitor end-to-end performance• Also monitor component performance

(individual links and devices)• Test reachability• Measure response times• Measure traffic flow and volume• Record route changes

Security Management• Maintain and distribute user names and

passwords• Generate, distribute, and store encryption keys• Analyze router, switch, and server

configurations for compliance with security policies and procedures

• Collect, store, and examine security audit logs

Network Management Components

• A managed device is a network node that collects and stores management information

• An agent is network-management software that resides in a managed device

• A network-management system (NMS) runs applications to display management data, monitor and control managed devices, and communicate with agents

Network Management ArchitectureNMS

Management Database

Agent

Management Database

Agent

Management Database

Agent

Managed Devices

Architecture Concerns

• In-band versus out-of-band monitoring– In-band is easier to develop, but results in

management data being impacted by network problems

• Centralized versus distributed monitoring– Centralized management is simpler to develop

and maintain, but may require huge amounts of information to travel back to a centralized network operations center (NOC)

Simple Network Management Protocol (SNMP)

• Most popular network management protocol• SNMPv3 should gradually supplant

(substitute) versions 1 and 2 because it offers better authentication and better control of the set command.

• SNMP works with Management Information Bases (MIBs).

Simple Network Management Protocol (SNMP)

What is a MIB? A MIB (Management Information Base) is a text

file which has been written using the ASN.1 (Abstract Syntax Notation) format. This text file is human readable but is special in that it can be compiled by a computer program called a MIB compiler, and then will result in creation of objects called OIDS (Object Identifiers), that can be understood by a network management station using the SNMP (Simple Network Management Protocol) method of communication.

Simple Network Management Protocol (SNMP)

Why is this important? SNMP MIBs are crucial in order to manage your

network and understand the underlying objects which are being retrieved from SNMP Agents. 

Remote Monitoring (RMON)

• Developed by the IETF in the early 1990s to address shortcomings in standard MIBs– Provides information on data link and physical

layer parameters– Nine groups of data for Ethernet– The statistics group tracks packets, octets, packet-

size distribution, broadcasts, collisions, dropped packets, fragments, CRC and alignment errors, jabbers, and undersized and oversized packets

Cisco Tools• Cisco Discovery Protocol– With the show cdp neighbors detail command, you

can display detailed information about neighboring routers and switches, including which protocols are enabled, network addresses for enabled protocols, the number and types of interfaces, the type of platform and its capabilities, and the version of Cisco IOS Software running on the neighbor.

• NetFlow Accounting– An integral part of Cisco IOS Software that collects and

measures data as it enters router or switch interfaces

Summary• Use a top-down approach– Chapter 2 talks about identifying assets and risks

and developing security requirements– Chapter 5 talks about logical design for security

(secure topologies)– Chapter 8 talks about the security plan, policy, and

procedures– Chapter 8 also covers security mechanisms and

selecting the right mechanisms for the different components of a modular network design

Summary• Determine which resources to monitor, which

data about these resources to collect, and how to interpret that data

• Develop processes that address performance, fault, configuration, security, and accounting management

• Develop a network management architecture• Select management protocols and tools

Review Questions• How does a security plan differ from a security policy?• Why is it important to achieve buy-in from users,

managers, and technical staff for the security policy?• What are some methods for keeping hackers from

viewing and changing router and switch configuration information?

• How can a network manager secure a wireless network?

Review Questions• Why is network management design important? • Define the five types of network management

processes according to the ISO. • What are some advantages and disadvantages of

using in-band network management versus out-of-band network management?

• What are some advantages and disadvantages of using centralized network management versus distributed network management?

This Week’s Outcomes

• Security• Threats and Risks• Security Policy• Security Mechanisms• Wireless Security• SNMP

Due this week

• 4-2-2 – Cisco Networking Practical Experience– Basic Routing and LAN Switching Configuration

Next week

• Read Chapter 8in Top-Down Network Design• – Concept questions 5

Q & A

• Questions, comments, concerns?