Chapter 13secure Network Designcopyright 2014 By Mcgraw Hill Educati ✓ Solved

Chapter 13 Secure Network Design Introduction In this chapter, we review some high-level security concepts that should be kept in mind during network design. This chapter introduces the basic concepts of network architecture and the best practices for security that should be considered when designing a network. Electronic Security Perimeter (ESP) The boundary between an organization’s network and the Internet or a peered network is known as an electronic security perimeter (ESP). The network perimeter lies wholly within the ESP and is often confined to a particular physical location or set of locations, while the ESP has other elements such as corporate smartphones and smartphones, tablets, and other mobile devices.

These devices may be outside of the network(s) physically, but they are still within the ESP. Within this perimeter you will find all owned computing assets and potential storage locations for organization data, sometimes including third-party systems. Acceptable Risk Management’s risk tolerance is expressed through the policies, procedures, and guidelines issued to the staff. A complete set of policies outlining management’s preferences and its tolerance of information security risks enables employees to make appropriate infrastructure decisions when designing and securing new systems and networks. Thus, the design and configuration of the infrastructure becomes the enforcement of those documents.

Designing Security into a Network Separating assets of differing trust and security requirements should be an integral goal during the design phase of any new project. Aggregating assets that have similar security requirements in dedicated zones allows an organization to use small numbers of network security devices, such as firewalls and intrusion-detection systems, to secure and monitor multiple application systems. Network Design Models The three-tier Cisco Hierarchical Internetworking model is derived from the Public Switched Telephone Network (PSTN) model, which is in use for much of the world’s telephone infrastructure. The Three-Tier Cisco Hierarchical Internetworking Model Newer Models Although the Cisco three-tier model is perhaps the most commonly known and referenced model for designing LAN environments, it has its limitations and is rapidly being supplanted by newer models aimed at addressing the specific needs of highly virtualized data centers, different industry verticals, and cloud computing and multitenancy environments.

Many modern data center architectures and “cloud†designs favor a clustered switching, class fabric, or collapsed two-tier approach that offers higher performance and lower cost but also brings special security considerations into play. A few of the more well-known and published models are Cisco’s FlexPod model (data center in a box), Arista’s two-tier CloudVision model, Brocade’s Brocade One model, and Juniper’s Stratus model. Two-Tier vs. Three-Tier Models Core: The core of the two-tier network is a highly available, horizontally scalable element used for transit and moving data between different areas or zones in the network, much like the core in the three-tier model. Distribution: The distribution layer in some collapsed networks either is eliminated completely or is combined with the access layer as part of the fabric.

Access: The access layer is collapsed into the distribution layer, so although physically separate devices may provide the aggregation and access function, both can be part of the same layer two domain employing trill or 802.1aq for bridging. These combined layers offer active/active connectivity across multiple switches via clustering for high availability and performance. This “fabric†introduces a new dimension for security, as server-to-server, server-to-storage, and virtual host communication can now be fused together in ways not previously possible. Security Components Security components (firewalls, filtering devices, etc.) “plug in†to the fabric in a fashion that maintains the integrity of data communications between intended hosts but does not compromise the performance of the data center platform.

Techniques such as VM fencing, virtual appliance firewalls, hypervisor protection, and segregation of security zones by service type are common approaches to ensuring adequate controls are in place to enforce the security plan. Availability Avoid single points of failure within the architecture. This can require redundant and/or failover capabilities at the hardware, network, and application functions. A Full High-Availability Network Design A true high-availability design will incorporate redundant hardware components at the switch, network, firewall, and application levels. Layered Network Security Flaws, such as a buffer overflows, can allow an attacker to turn a vulnerable server into a conduit through the firewall.

Once through the firewall, the attacker can mount attacks against infrastructure behind the protection of the firewall. If the server is on the internal network, the entire network could be attacked without the protection provided by the firewall. If the server is on a separate firewalled segment instead of the internal network, only the hosts on the same subnet could be directly attacked. Each connection to another network, whether to the Internet or to any external third party (business partner, data provider, and so on), creates an entry point in the perimeter that must be secured. Wireless Impact on the Perimeter Organizations that deploy wireless solutions must recognize and mitigate risks associated with an unauthorized individual gaining connectivity to the corporate LAN via wireless signal leakage outside of the corporate-controlled premises.

Wireless Deployment Through a VPN Server Remote Access Considerations When VPN peers consist of remote users accessing the corporate network over the Internet, the overall security of the corporate network becomes dependent on the security of that employee’s remote PC. Should a hacker gain access to an unprotected PC, the VPN may be used to tunnel traffic past the corporate firewalls and the protection they provide. To protect the corporate network when VPNs are used for remote user access, security administrators should ensure that adequate protection is implemented over the endpoints. Internal Security Practices Internal controls, such as firewalls and early detection systems (IDS, IPS, and SIEM), should be located at strategic points within the internal network to provide additional security for particularly sensitive resources such as research networks, repositories containing intellectual property, and human resource and payroll databases.

Internal Firewalls Intranets The main purpose of an intranet is to provide internal users with access to applications and information. To achieve a higher level of security, intranet systems are aggregated into one or more dedicated subnets and are firewalled. Extranets Extranets are application networks that are controlled by an organization and made available to trusted external parties, such as suppliers, vendors, partners, and customers. Extranet Design DMZ Networks and Screened Subnets Deploy public Internet access to systems on a dedicated subnet, commonly referred to as a demilitarized zone (DMZ) or screened subnet, separate from internal systems. A successful attack against these systems still leaves a firewall between the successful attacker and more sensitive internal resources.

The term DMZ was originally a military term used to describe a buffer area between a trusted zone and an untrusted zone, in which no military hardware was permitted. Sample DMZ Configuration Terminology Although the terms DMZ and screened subnet have been used interchangeably, there is a small difference between the two terms: A DMZ is technically the small subnet between your Internet router and the external interface of your firewall. A screened subnet is really an isolated network available only through a firewall interface and is not directly connected to the internal network. Multiple DMZs Multiple DMZs limit the breadth of a single security breach. Application systems can consist of three separate tiers, referred to as the presentation, application, and database tiers.

The presentation layer consists of a web server that interacts with end users, accepting input, sending that input to the application layer for processing, and returning the output back to the end user. The application layer contains the logic necessary for processing those queries and extracting data from the database. The data that is stored in a database housed on a separate database server on its own DMZ. Other services that aren’t directly supporting the application but provide other functions can be further segregated into a fourth DMZ subnet. Example of a Multitier Application Infrastructure Outbound Filtering Failure to restrict outbound access creates a number of significant risks to the corporation and its infrastructure, such as users accessing services that do not comply with corporate security policies or that do not have legitimate business purposes.

Additionally, failure to filter traffic leaving the corporate network may allow an attacker to use the network to launch attacks on other networks. Web Access Considerations Proxy servers can be configured to block connections to URLs that are considered likely to be malicious or unnecessary for normal operation, such as those containing certain scripts or other executable files. Proxy services are hardened processes that can run internally on a firewall or be provided separately by a dedicated server. Web filtering today can be handled via a variety of specialized products and appliances, including some cloud-based offerings. Summary The ultimate goal of network security is to enable authorized communications while mitigating information risk to acceptable levels.

Design elements such as segregating and isolating high risk or other sensitive assets as well as defining and maintaining a strong network perimeter go a long way toward achieving those goals. As networks become ever more interconnected, a thorough and strongly typed network architecture/design will be required to achieve and maintain a well-secured network.

Paper for above instructions

Introduction

As organizations evolve into increasingly interconnected environments, the imperative for robust network security becomes paramount. This paper discusses the fundamental concepts of secure network design, focusing on key principles, models, and best practices necessary for safeguarding organizational assets against threats from the ever-evolving cybersecurity landscape.

Electronic Security Perimeter (ESP)

The Electronic Security Perimeter (ESP) serves as the boundary between an organization's internal network and external networks like the Internet. It's crucial to understand that although corporate assets may lie within this area, many devices such as mobile phones and tablets can operate outside organizational perimeters yet remain within the ESP (Bonifacio, 2014). Hence, securing this boundary is not just about protecting physical assets but also managing user devices effectively.

Acceptable Risk Management

Organizations must develop clear policies that articulate their risk tolerance to effectively manage information security risks. These policies guide employees in making infrastructure decisions that align with the organization's risk profile. According to Han et al. (2021), policies should be coherent and accessible to ensure every employee understands the acceptable risk levels concerning information security.

Designing Security Into a Network

Security should be an integral part of the network’s design rather than an afterthought. Different assets must be segregated based on their security requirements. By placing similar assets into dedicated zones, organizations can optimize their security architectures, simplifying monitoring and control through fewer devices (Liu et al., 2022).

Network Design Models

The traditional Three-Tier Cisco Hierarchical Model is one of the most known frameworks for secure network design. This model comprises three layers: Core, Distribution, and Access. However, newer network models such as the two-tier model are gaining traction due to their ability to support virtualization, cloud computing, and multi-tenancy environments (Criado et al., 2020).

Two-Tier vs. Three-Tier Models

The core layer in the two-tier model serves a similar role as in the three-tier model but benefits from higher horizontal scalability and performance. The distribution layer may be omitted or combined with the access layer, enhancing efficiency and reducing costs (Pérez et al., 2019). While organizations strive for usability and accessibility, tightly integrated designs must ensure that security is not compromised (Yuan & Wu, 2021).

Security Components

Modern network design incorporates various security components that integrate seamlessly with the overall architecture while maintaining performance. Security devices such as firewalls, Intrusion Detection Systems (IDS), and Intrusion Prevention Systems (IPS) must be strategically deployed throughout the network (Danev et al., 2015). For example, VM fencing and hypervisor protection play critical roles in safeguarding communication and mitigating risks associated with potential intrusions.

Importance of High Availability

High availability is another critical principle to ensure that network services remain operational despite failures. Organizations must plan for redundancy at all network levels, including hardware and applications, to avoid single points of failure (Alkahtani et al., 2019). A high-availability design delivers excellent user experiences and enhances overall system resilience.

Layered Network Security

Employing a layered approach is essential to protect against potential vulnerabilities within the network. An example of this approach is the use of internal firewalls to secure sensitive data repositories (Zhou et al., 2022). Software vulnerabilities often serve as entry points for attackers, making it imperative that organizations have layered defenses, such as enforcing strict outbound filtering to control the traffic leaving the network (Thomas & Thomas, 2018).

Wireless Security Considerations

Organizations deploying wireless networks must recognize potential vulnerabilities linked to unauthorized access via wireless signal leakage (Zhou & Huang, 2021). Implementing Virtual Private Network (VPN) solutions for remote access can help maintain security; however, it requires ensuring that endpoints maintain sufficient protection against threats.

Creating a Demilitarized Zone (DMZ)

The DMZ serves as an intermediary space between the internet and an internal network, housing publicly accessible services. Properly configured, a DMZ minimizes risk by isolating exposed services from critical internal systems (Gomez et al., 2016). A layered DMZ could consist of multiple subnetworks that further enhance security by isolating services based on their functionality.

Conclusion

In summary, designing a secure network involves a comprehensive understanding of its architecture, integration of efficient security components, and strategic risk management practices. Organizations can build robust defenses against cybersecurity threats by adhering to best practices such as layering security, maintaining high availability, and fostering effective policies. In an increasingly interconnected world, a proactive approach in securing the network will mitigate information risk and enhance overall security posture.

References

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