Container Security in 2014: Why Your Docker Strategy is a Ticking Time Bomb

Let’s be honest with each other. We are all excited about Docker 1.3. The ability to ship code from a developer's laptop to production without "dependency hell" is intoxicating. But if you are blindly throwing containers onto a bare-metal server and opening port 80, you aren't a DevOps engineer; you're a liability.

I recently audited a setup for a client in Oslo—a promising e-commerce startup. They had their entire payment processing pipeline running inside unprivileged containers on a single host. No AppArmor profiles. Default networking. And the Docker daemon running as root. One kernel exploit, and that attacker wouldn't just be inside a container; they would own the metal, the data, and the backups.

Containerization is the future, but in 2014, the security model is still the Wild West. Here is how you lock it down before you get paged at 3 AM.

The "Shared Kernel" Trap

The fundamental difference between a Virtual Machine (VM) and a Container is the kernel. In a VM, you have a hypervisor (like KVM or Xen) and a completely separate kernel. In a container (LXC/Docker), you are sharing the host's kernel. Namespaces and cgroups are clever lies we tell processes to make them think they are alone. But they aren't.

If you rely solely on container isolation, you are betting your entire infrastructure that there are no bugs in the Linux 3.x kernel. That is a bad bet.

The Solution: Nesting on KVM

This is where architecture matters. The safest way to run containers today is inside a robust KVM-based VPS. If a container breaks out, it only compromises that specific VM, not the host node and certainly not your neighbor's data.

Pro Tip: This is why CoolVDS is built strictly on KVM virtualization. We don't use OpenVZ or other container-based virtualization for our core VPS offerings because we believe in hard hardware virtualization boundaries. You get your own kernel. Break it if you want; it won't hurt us.

Hardening the Container Runtime

If you must run Docker (and let's face it, we all want to), you need to restrict what it can do. By default, Docker containers are granted a frightening amount of capabilities.

1. Drop Capabilities

Most web applications do not need to change the system time or modify network interfaces. Drop everything and add back only what is necessary.

docker run --cap-drop=ALL --cap-add=NET_BIND_SERVICE --cap-add=SETUID www-node-app

2. Read-Only Filesystems

Immutability is your friend. If an attacker manages to exploit your Nginx or Apache process, the first thing they will try to do is download a payload or modify a config file. Don't let them.

docker run --read-only -v /my/data:/data:rw my-app

This forces the root filesystem of the container to be read-only. Any state must be written to the mounted volume /data. It’s a simple flag that kills 90% of script-kiddie exploits.

Network Segregation with iptables

Docker's bridge networking is convenient, but it can be chatty. By default, containers can talk to each other. If you have a compromised frontend container, it shouldn't be able to scan your database container unless explicitly allowed.

We need to get our hands dirty with iptables. Do not rely on the daemon to do this for you.

# Create a custom chain for Docker traffic
iptables -N DOCKER-USER

# Allow established connections
iptables -A DOCKER-USER -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT

# Drop traffic between containers on the same bridge by default
iptables -A DOCKER-USER -i docker0 -o docker0 -j DROP

The Norwegian Context: Data Sovereignty

We are seeing stricter enforcement from Datatilsynet (The Norwegian Data Protection Authority). With the current Safe Harbor framework under scrutiny and the Data Protection Directive requiring tight control over personal data, knowing exactly where your bits live is non-negotiable.

Latency is another factor often ignored by the "cloud is magic" crowd. If your users are in Scandinavia, routing traffic to a data center in Virginia is a performance crime. The speed of light is constant.

Performance: The I/O Bottleneck

Containers generate a lot of small, random I/O operations, especially during build and tear-down phases. Traditional spinning rust (HDD) cannot handle the random read/write patterns of a busy Docker registry or a high-traffic database container.

At CoolVDS, we are currently testing the new NVMe storage technology in our labs. While standard enterprise SSDs are fast, NVMe connects directly to the PCIe bus, bypassing the SATA bottleneck entirely. It is the future of low latency hosting, and for I/O heavy container workloads, it effectively eliminates "iowait" as a metric you need to watch.

Final Thoughts

Security is not a product you buy; it's a process you adhere to. In late 2014, the tools for container orchestration are still immature. Kubernetes is barely an alpha concept, and fleet management is manual work. This puts the burden on you, the Systems Administrator, to configure the underlying host correctly.

Start with a solid foundation. You need a host that respects data privacy, offers massive DDoS protection (because NTP reflection attacks are not going away), and provides the raw I/O performance your containers demand.

Don't let your infrastructure be the reason your startup fails. Deploy a hardened KVM instance on CoolVDS today and experience the stability of true hardware isolation.