Security for Cloud-based Enterprise Applications

Being the architect of a cloud-based enterprise software-as-a-service (SaaS) product — Adobe LiveCycle Express — I get asked a lot about the security of cloud-based applications. They are all the questions you would expect: “Is my data secure in the cloud?”; “How safe are cloud service environments?; “Aren’t you just asking to be hacked?”. My response to all of these questions is, first, to tell them to take a deep breath and relax, and second, to think of the cloud as any other computer system faced with security threats, and for which you need to develop a threat response. Security for cloud-based applications is actually a multifaceted problem, with distinct threats and responses for network security, operating system security, data security, and virtualization security — but each of these distinct areas has an analog in non-cloud-based applications that has been analyzed and for which there are security procedures to help reduce threats. So, ultimately, we just need to ignore the hype surrounding cloud computing and focus on the fundamental computer system security issues that applications will face in this domain. Some brief commentary on each of the threat areas faced by cloud-based applications follows, along with a note about regulatory issues. As with anything you read on the internet, your mileage may vary.

Network Security for Cloud-based Enterprise Applications

The ideal network security paradigm for cloud-based enterprise applications would be to have the cloud services be an extension of the customer’s existing internal networks, using all of the same protection measures and security precautions that their administrators have developed. This implies a strategy that would allow a customer to extend their network security envelope to encompass the cloud services that they use. For my application, I have chosen to use an encrypted TCP port forwarding strategy to extend the customer’s network security envelope into the cloud. Specifically, I use an implementation of the ssh protocol that performs bi-directional TCP traffic forwarding across encrypted, compressed connections between cloud-based virtual instances and customer machines behind their corporate firewalls. The encryption strength is configurable, and is at least as secure as any corporate VPN encryption. This is another way of saying that it does not introduce any new network threats beyond what a customer already faces with their existing VPN technologies. Less paranoid customers can choose to downgrade the security of their cloud instances and access them directly via HTTP and HTTPS, but my recommended approach is to use encrypted traffic forwarding, both for robust security and to translate the problem of cloud-based network security into terms and concepts — VPNs and encryption — that system administrators will understand. In reducing the problem of cloud-based network security to one of corporate network security, we simplify the problem of assessing and responding to cloud-based network security threats.

Operating System Security for Cloud-based Enterprise Applications

Cloud-based virtual instances face the same OS-level threats as standard hardware-based installs. The typical responses for these threats are the same as for hardware-based installs (e.g. block all non-essential listen ports via firewalls, keep the OS patches current, and run modern anti-virus software). For my enterprise application, I recommend that all ports except the ssh port (port 22) are to be blocked by firewall, patches are to be updated periodically and rolled into new virtual images, and antivirus software is to be installed; these measures collectively ensure that the virtual instances face no new OS-level threats beyond what a customer already faces with their existing hardware. As with network security, by reducing the problem of cloud-based operating system security to one of traditional hardware-based operating system security we simplify the problem of assessing and responding to threats.

Data Security for Cloud-based Enterprise Applications

In cloud-based applications, data encryption is the simplest way to protect data. Data in a cloud-based application will likely be transiting public networks and shared resources, and it makes sense to protect it against simple observation. Modern encryption technologies will withstand all but the most determined attempts to crack them, and while they require some key sharing infrastructure to implement them properly, they can be deployed using traditional methods employed for non-cloud-based applications. There are potential performance implications for data encryption, but, in my opinion, when using modern hardware and fast networks with a well-designed application, the performance implications can be effectively minimized. In my application, virtual instances store their backups off-instance within a cloud storage service. These backups are encrypted using a PKI key pair, with only the public key stored on the virtual instance. The data storage needs of virtual instances in my application are simple and infrequent, so the application easily lends itself to a data encryption strategy. Not all applications will have these characteristics; however, there are very few alternatives that can ensure data security in cloud-based applications. Thus, data encryption in some form will likely be a necessary evil of all cloud-based applications…but it’s not really that evil. And once again, we have reduced the problem of data security in cloud-based applications to an existing, non-cloud-based technology domain.

Virtualization Security for Cloud-based Enterprise Applications

Cloud-based virtual instances face resource-sharing threats that are inherent to the virtualization environment. These threats, however, are similar to the resource-sharing threats seen by enterprise applications that share hardware resources, either by design or necessity, within corporate data centers, and for which there are some procedures and assumptions that can be put to use in the cloud domain. For cloud-based resource-sharing threats, the problem is largely within the domain of the cloud virtualization provider, and it is their responsibility to respond to the threat. Customers of a virtualization service are ultimately trusting the virtualization service provider to guarantee the inter-instance security of the virtual instances, much as shared applications on common hardware are trusting the operating system to enforce inter-process security. Cloud-based applications rely on cloud services to enforce inter-instance security and guarantee that shared memory and disk resources can not be used to access another customer’s applications. Many cloud service providers run their own business applications within the same virtualization fabric, so it is fair to assume that inter-instance security is being monitored by corporate security professionals. In my opinion, the security budgets of the major cloud service providers far exceeds the security budgets of most cloud service consumers, and thus the degree of virtualization security provided in these service environments will be at least as good as the resource-sharing security found within a customer’s data center. For example, Amazon runs their flagship business within the same data centers as their cloud services, and I imagine that they have some of the best security professionals in the industry ensuring that their business applications are not at risk to resource-sharing threats from their cloud services. Ultimately, however, the threat is not substantially different than the hardware-based shared resource threats that customers currently face in their own datacenters. We can reduce the issue of virtualization security to one that is similar to an existing threat, and for which there are standard practices to assess and respond to that threat.

Regulatory Issues for Cloud-based Enterprise Applications

A discussion of security for cloud-based enterprise applications would not be complete without some comments on the regulatory issues that come into play when enterprise applications, and specifically enterprise application data, are moved into cloud-based services. Legislation and regulation in many industries has led to strict guidelines regarding enterprise data, primarily to protect the privacy of individuals. For example, The Health Insurance Portability and Accountability Act (HIPAA) contains strict provisions on what can be done with individuals’ health records, and what permissions must be explicitly received from those individuals for any transfer of those records. For an enterprise application that contains health records, this presents an open question that must be answered before that application can integrate cloud services into its architecture: How do the regulations within HIPAA apply to cloud-based services, and what restrictions do they place, if any, upon the use of third-party cloud services within enterprise healthcare applications? The answer to this question, and similar questions for regulations in other industries, is evolving rapidly, but it will ultimately be answered by legislation and regulation rather than by technology. However, progress towards an answer will be made by software vendors and enterprise customers that make the case that threats faced by cloud-based enterprise applications are ultimately no different, and no more severe, than the existing threats faced by those applications in their current deployment formats.


I have tried to make the argument that the security threats seen by cloud-based enterprise applications are translations of threats seen by existing enterprise applications within corporate data centers, and thus there are existing procedures and responses that can be put to use in designing an appropriate security strategy. To paraphrase Bruce Schneier, security is theater, and the perception of security for cloud-based enterprise applications is likely more important than the actual manifestation of the security mechanisms. This has been true at each evolutionary stage for enterprise systems — does everyone remember the paranoia surrounding the first attempts to connect corporate networks to the public internet? — and the continuing deployment of ever more cloud-based applications will need to reach a critical mass, with respect to the perceived security story, before it becomes effectively mainstream. But that day is coming.

Hope this helps.