We often get requests for best practices related to relational database security in the context of cloud computing. People want to install their database of choice, whether it be Oracle, MySQL, MS SQL, or IBM DB2…

This is a complex question but it can be broken down by asking “what’s new in the cloud?” Many techniques that have existed for ages remain important, so let’s briefly review database security in general.

Database Security in Context
A database usually does not stand alone; it needs to be regarded in the light of the environment it inhabits. From the security perspective, it pays to stop and think about:

• Application security. The application which uses the database (“sits atop” the DB) is itself open to various attacks. Securing the application will close major attack vectors to the data, such as SQL injection
• Physical security. In the cloud context, it means choose a cloud provider that has implemented and documented security best practices
• Network security. Your cloud environment and 3^rd part security software should include network security techniques such as firewalls, virtual private networks, and intrusion detection and prevention
• Host security. In the cloud, your instances (a.k.a virtual servers) should use an up-to-date and patched operating system, virus and malware protection, and monitor and log all activities

Having secured everything outside the database, you are still left with threats to the database itself. They often involve:

• Direct attacks on the data itself (in an attempt to get at it)
• Indirect attacks on the data (such as at the log files)
• Attempts to tamper with configuration
• Attempts to tamper with audit mechanisms
• Attempts to tamper with the DB software itself (e.g. tamper with the executables of the database software)

So far, these threats are recognizable to any database security expert with years of experience in the data center. So what changes in the cloud?

Data at Rest in the Cloud
At the end of the day, databases save “everything” on disks, often in files that may represent tables, configuration information, executable binaries, or other logical entities.

Defending and limiting access to these files is of course key. In the “old” data center, this was usually done by placing the disks in a (hopefully) secure location, i.e. in a room with good walls and restricted access. In the cloud, virtual disks are accessible through a browser, and also to some of the employees of the cloud provider; obviously some additional thinking is required to secure them.

Besides keeping your access credentials closely guarded, it is universally recommended that virtual disks with sensitive data should always be encrypted.

There are two basic ways to defend these files:

• File-level encryption. Basically you need to know which specific files you wish to protect, and encrypt them by an appropriate technique
• Full disk encryption. This encrypts everything on the disks

Full disk encryption today is the best practice. It ensures nothing is forgotten.

Encryption Keys in the Cloud
Encrypting your data at rest on virtual disks is definitely the right way to go. You should also consider were the encryption keys are kept, since if an attacker gets hold of the keys they will be able to decrypt your data.

It is recommended to avoid solutions that keep your keys right next to your data, since then you actually have no security.

It is also recommended to avoid vendors that tell you “don’t trust the cloud, but trust us, and let us save your keys”. There are a number of such vendors in the market. The fact is that cloud providers such as Amazon, Microsoft, Rackspace or Google – know their stuff. If you do not trust them with your precious data, why trust cloud vendor X?

One approach that does work from a security perspective – you can keep all your keys back in your data center. But that is cumbersome; in fact you went out to the cloud because you wanted to move out of the data center.

A unique solution does exist. Porticor provides its unique key management solution which allows you to trust no one but yourself, yet enjoy the full power of a pure cloud implementation. For more on this, see this white paper. This solution also fully implements full disk encryption, as noted above.

Database security in the cloud is a complex subject, yet entirely possible today.

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