Transcript Key Device
Secure Network Design Lecture 10 Asst.Prof.Supakorn Kungpisdan, Ph.D. [email protected] NETE4630 Advanced Network Security and Implementation Network Security Design: The 12 Step Program 1. Identify network assets 7. Achieve buy-in from users, managers, and technical staff 2. Analyze security risks 3. Analyze security requirements and tradeoffs 8. Train users, managers, and technical staff 4. Develop a security plan 9. 5. Define a security policy Implement the technical strategy and security procedures 6. Develop procedures for applying security policies 10. Test the security and update it if any problems are found 7. Develop a technical implementation strategy 11. Maintain security 2 NETE4630 Advanced Network Security and Implementation Network Assets Hardware Software Applications Data Intellectual property Trade secrets Company’s reputation 3 NETE4630 Advanced Network Security and Implementation 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 Denial-of-service attacks 4 NETE4630 Advanced Network Security and Implementation Security Tradeoffs Tradeoffs must be made between security goals and other goals: Affordability Usability Performance Availability Manageability 5 NETE4630 Advanced Network Security and Implementation A Security Plan High-level document that proposes what an organization is going to do to meet security requirements It specifies time, people, and other resources that will be required to develop a security policy and achieve implementation of the policy 6 NETE4630 Advanced Network Security and Implementation 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 7 NETE4630 Advanced Network Security and Implementation Security Mechanisms Physical security Authentication Authorization Accounting (Auditing) Data encryption Packet filters Firewalls Intrusion Detection Systems (IDSs) 8 NETE4630 Advanced Network Security and Implementation Modularizing Security Design Security defense in depth Network security should be multilayered with many different techniques used to protect the network Belt-and-suspenders approach Don’t get caught with your pants down 9 NETE4630 Advanced Network Security and Implementation 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 10 NETE4630 Advanced Network Security and Implementation Cisco’s Enterprise Composite Network Model Enterprise Campus Network Management Building Distribution Campus Backbone Server Farm Campus Infrastructure Building Access Enterprise Edge E-Commerce Edge Distribution Internet Connectivity VPN/ Remote Access Service Provider Edge ISP A ISP B PSTN Frame Relay, ATM WAN 11 NETE4630 Advanced Network Security and Implementation Cisco SAFE Cisco SAFE Blueprint addresses security in every module of a modular network architecture. 12 NETE4630 Advanced Network Security and Implementation Legend 13 NETE4630 Advanced Network Security and Implementation SAFE Block Diagram 14 NETE4630 Advanced Network Security and Implementation Enterprise Campus Details 15 NETE4630 Advanced Network Security and Implementation Management Module The primary goal of the management module is to facilitate the secure management of all devices and hosts within the enterprise SAFE architecture. Logging and reporting information flow from the devices through to the management hosts, while content, configurations, and new software flow to the devices from the management hosts. 16 NETE4630 Advanced Network Security and Implementation Management Module Key Devices SNMP Management host – provides SNMP management for devices NIDS host – provides alarm aggregation for all NIDS devices in the network System Admin host – provides configuration, software, and content changes on devices NIDS appliance – provides Layer 4 to Layer 7 monitoring of key network segments in the module Cisco IOS Firewall – allows granular control for traffic flows between the management hosts and the managed devices Layer 2 switch (with private VLAN support) – ensures data from managed devices can only cross directly to the IOS firewall Syslog host(s) – aggregates log information for Firewall and NIDS hosts Access Control Server – delivers onetime, two-factor authentication services to the network devices One-Time Password (OTP) Server – authorizes one-time password information relayed from the access control server 17 NETE4630 Advanced Network Security and Implementation Management Module Details 18 NETE4630 Advanced Network Security and Implementation Threats Mitigated Unauthorized Access – filtering at the IOS firewall stops most unauthorized traffic in both directions Man-in-the-Middle Attacks – management data is crossing a private network making man-in-the-middle attacks difficult Network Reconnaissance – because all management traffic crosses this network, it does not cross the production network where it could be intercepted Password Attacks – the access control server allows for strong two-factor authentication at each device IP Spoofing – spoofed traffic is stopped in both directions at the IOS firewall Packet Sniffers – a switched infrastructure limits the effectiveness of sniffing Trust Exploitation – private VLANs prevent a compromised device from masquerading as a management host 19 NETE4630 Advanced Network Security and Implementation Attack Mitigation Roles for Management Module 20 NETE4630 Advanced Network Security and Implementation Core Module Key Device: Layer 3 switching – route and switch production network data from one module to another Threats Mitigated: Packet Sniffers – a switched infrastructure limits the effectiveness of sniffing 21 NETE4630 Advanced Network Security and Implementation Building Distribution Module To provide distribution layer services to the building switches; these include routing, quality of service (QoS), and access control. Key Device: Layer 3 switches – aggregate Layer 2 switches in building module and provide advanced services Threats Mitigated Unauthorized Access – attacks against server module resources are limited by Layer 3 filtering of specific subnets IP Spoofing Packet Sniffers – a switched infrastructure limits the effectiveness of sniffing 22 NETE4630 Advanced Network Security and Implementation Building Module SAFE defines the building module as the extensive network portion that contains end-user workstations, phones, and their associated Layer 2 access points. Its primary goal is to provide services to end users. Key Devices Layer 2 switch – provides Layer 2 services to phones and user workstations User workstation – provides data services to authorized users on the network IP phone – provides IP telephony services to users on the network Threats Mitigated Packet sniffers – a switched infrastructure and default VLAN services limit the effectiveness of sniffing Virus and Trojan horse applications – host-based virus scanning prevents most viruses and many Trojan horses 23 NETE4630 Advanced Network Security and Implementation Server Module To provide application services to end users and devices. Traffic flows on the server module are inspected by on-board intrusion detection within the Layer 3 switches. Key Devices L3 Switch – provides layer three services to the servers and inspects data crossing the server module with NIDS Call Manager – performs call routing functions for IP telephony devices in the enterprise Corporate and Department Servers – delivers file, print, and DNS services to workstations in the building module E-Mail Server – provide SMTP and POP3 services to internal users Threats Mitigated Unauthorized Access Application Layer Attacks IP Spoofing Packet Sniffers Trust Exploitation Port Redirection 24 NETE4630 Advanced Network Security and Implementation Edge Distribution Module To aggregate the connectivity from the various elements at the edge. Key Devices: Layer 3 switches – aggregate edge connectivity and provide advanced services Threats Mitigated Unauthorized Access – filtering provides granular control over specific edge subnets and their ability to reach areas within the campus IP Spoofing – RFC 2827 filtering limits locally initiated spoof attacks Network Reconnaissance – filtering limits nonessential traffic from entering the campus limiting a hackers ability to perform network recon Packet Sniffers – a switched infrastructure limits the effectiveness of sniffing 25 NETE4630 Advanced Network Security and Implementation Enterprise Edge Corporate Internet Module 26 Enterprise Edge NETE4630 Advanced Network Security and Implementation Corporate Internet Module Key Devices SMTP server – acts as a relay between the Internet and the Internet mail servers – inspects content DNS server – serves as authoritative external DNS server for the enterprise, relays internal requests to the Internet FTP/HTTP server – provides public information about the organization Firewall – provides network-level protection of resources and stateful filtering of traffic NIDS appliance – provides Layer 4 to Layer 7 monitoring of key network segments in the module URL Filtering Server – filters unauthorized URL requests from the enterprise Threats Mitigated Unauthorized Access – mitigated through filtering at the ISP, edge router, and corporate firewall Application Layer Attacks – mitigated through IDS at the host and network levels Virus and Trojan Horse – mitigated through e-mail content filtering and host IDS Password Attacks – limited services available to brute force, OS and IDS Denial of Service IP Spoofing –at ISP edge and enterprise edge router Packet Sniffers – switched infrastructure and host IDS limits exposure Network Reconnaissance – IDS detects recon, protocols filtered to limit effectiveness Trust Exploitation – restrictive trust model and private VLANs limit trust-based attacks Port Redirection – restrictive filtering and host IDS limit attack 27 NETE4630 Advanced Network Security and Implementation Attack Mitigation Role for Corporate Internet Module 28 NETE4630 Advanced Network Security and Implementation Enterprise Edge Remote Access VPN Module The primary objective of this module is three-fold: Terminate the VPN traffic from remote users Provide a hub for terminating VPN traffic from remote sites, and Terminate traditional dial-in users. 29 NETE4630 Advanced Network Security and Implementation Enterprise Edge Remote Access VPN Module (cont.) Key Devices VPN Concentrator – authenticate individual remote users using Extended Authentication (XAUTH) and terminate their IPSec tunnels VPN Router – authenticate trusted remote sites and provide connectivity using GRE/IPSec tunnels Dial-In Server – authenticate individual remote users using TACACS+ and terminate their analog connections Firewall – provide differentiated security for the three different types of remote access NIDS appliance – provide Layer 4 to Layer 7 monitoring of key network segments in the module Threats Mitigated Network Topology Discovery – only Internet Key Exchange (IKE) and Encapsulating Security Payload (ESP) are allowed into this segment from the Internet Password Attack – OTP authentication reduces the likelihood of a successful password attack Unauthorized Access – firewall services after packet decryption prevent traffic on unauthorized ports Man-in-the-Middle – mitigated through encrypted remote traffic Packet Sniffers – a switched infrastructure limits the effectiveness of sniffing 30 NETE4630 Advanced Network Security and Implementation Attack Mitigation Roles for Remote Access VPN Module 31 NETE4630 Advanced Network Security and Implementation Enterprise Edge WAN Module Rather than being all-inclusive of potential WAN designs, this module shows resilience and security for WAN termination. Key Devices: IOS Router – using routing, access-control, QoS mechanisms Threats Mitigated IP Spoofing – mitigated through L3 filtering Unauthorized Access – simple access control on the router can limit the types of protocols to which branches have access 32 NETE4630 Advanced Network Security and Implementation Enterprise Edge E-Commerce Module 33 NETE4630 Advanced Network Security and Implementation Securing Internet Connections Physical security Firewalls and packet filters Audit logs, authentication, authorization Well-defined exit and entry points Routing protocols that support authentication 34 NETE4630 Advanced Network Security and Implementation Securing Public Servers Place servers in a DMZ that is protected via firewalls Run a firewall on the server itself Enable DoS 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 35 NETE4630 Advanced Network Security and Implementation Security Topologies Enterprise Network DMZ Internet Web, File, DNS, Mail Servers 36 NETE4630 Advanced Network Security and Implementation Security Topologies Internet Firewall DMZ Enterprise Network Web, File, DNS, Mail Servers 37 NETE4630 Advanced Network Security and Implementation Securing Remote-Access and Virtual Private Networks Physical security Firewalls Authentication, authorization, and auditing Encryption One-time passwords Security protocols CHAP RADIUS IPSec 38 NETE4630 Advanced Network Security and Implementation 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 rather than Telnet Change the welcome banner to be less welcoming 39 NETE4630 Advanced Network Security and Implementation 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 40 NETE4630 Advanced Network Security and Implementation 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 41 NETE4630 Advanced Network Security and Implementation 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 42 NETE4630 Advanced Network Security and Implementation WLAN Security Options Wired Equivalent Privacy (WEP) 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? 43 NETE4630 Advanced Network Security and Implementation 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 crackable 44 NETE4630 Advanced Network Security and Implementation 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 Wi-Fi Protected Access (WPA) from the Wi-Fi Alliance Realistic parts of IEEE 802.11i now! 45 NETE4630 Advanced Network Security and Implementation VPN Software on Wireless Clients 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 46 NETE4630 Advanced Network Security and Implementation 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? How can a network manager secure a wireless network? 47