Cloud Application Architectures

Host Security

Host security describes how your server is set up for the following tasks:

• Preventing attacks.

• Minimizing the impact of a successful attack on the overall system.

• Responding to attacks when they occur.

It always helps to have software with no security holes. Good luck with that! In the real world, the best approach for preventing attacks is to assume your software has security holes. As I noted earlier in this chapter, each service you run on a host presents a distinct attack vector into the host. The more attack vectors, the more likely an attacker will find one with a security exploit. You must therefore minimize the different kinds of software running on a server.

Given the assumption that your services are vulnerable, your most significant tool in preventing attackers from exploiting a vulnerability once it becomes known is the rapid rollout of security patches. Here’s where the dynamic nature of the cloud really alters what you can do from a security perspective. In a traditional data center, rolling out security patches across an entire infrastructure is time-consuming and risky. In the cloud, rolling out a patch across the infrastructure takes three simple steps:

1. Patch your AMI with the new security fixes.

2. Test the results.

3. Relaunch your virtual servers.

Here a tool such as enStratus or RightScale for managing your infrastructure becomes absolutely critical. If you have to manually perform these three steps, the cloud can become a horrible maintenance headache. Management ...