Commerce
E-commerce design is discussed in the section titled "Three-Tier Web Design" in Chapter 8. Figures 8-8 and 8-9 show these designs using firewalls to act as choke points. Figure 13-13 shows the same design integrated with all the relevant security technology.
Figure 13-13. Three-Tier E-Commerce Design
Web Database
Servers Servers
Figure 13-13. Three-Tier E-Commerce Design
Web Database
Servers Servers
If your application and database layers don't have a clean way to separate, you can optionally use the two-tier design discussed in Chapter 8. This design is less secure but significantly reduces the cost of the infrastructure.
All organizations should strongly consider outsourcing the e-commerce network or housing their own e-commerce environments in a collocation facility. Both options increase the bandwidth available to your customers and so increase the DDoS attack requirements to take your network out of service. Just be sure you have a secure way to manage these systems and make content modifications.
NIDS (both anomaly and signature based) can help detect many forms of attack, as shown earlier in this chapter. In addition, host security controls are as important as ever. In your e-commerce environment, server load balancing, Secure Sockets Layer (SSL) offload, or some form of caching might be needed. Chapter 11 provides information on these three topics.
The firewalls and NIDS devices at each tier of the design should be tightly configured, as shown in Chapter 8. Because the traffic types are very well known, it becomes comparatively easy to spot attacks in your application and database tiers as compared to your general-use Internet edge.
Redundancy can be added to the design in Figure 13-13 with the same caveats already discussed in the high-end resilient edge design. It is also beneficial to use dedicated Internet bandwidth for your ecommerce traffic to allow for specific filtering as discussed in the "E-commerce Specific Filtering" section of Chapter 6.
One design to steer clear of is the "dual-homed-host" e-commerce design. I see this design occasionally when consulting with organizations. Although this design (which is usually a variation on Figure 13-14) can seem more secure at first appearance because application servers and database servers can be put on private internal networks with no ability to route to the outside, it is, unfortunately, a house of cards. A compromise in the initial web server allows all traffic types to attack the application server (from the web server). The application server can then launch the same attacks to the database server.
Figure 13-14. Dual-Homed-Host E-Commerce Design (Not Recommended)
Figure 13-14. Dual-Homed-Host E-Commerce Design (Not Recommended)
This contrasts with the design in Figure 13-13, which allows traffic flows only on very specific ports and protocols in the event that a server is compromised. Small networks looking for an e-commerce presence likely do not have the financial resources to deploy the e-commerce designs shown here. For these organizations, e-commerce can be hosted off of a public services segment (with the rest of your services) with the caveat that the security afforded will be much lower. A better option is to look for an e-commerce hosting provider that can provide a secure infrastructure for the Internet business.
Continue reading here: Stateful Versus Stateless ACLs and L3 Versus L4 Filtering
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