Six Essential Docker Security Best Practices for Safe Containers

Docker helps you launch new apps in minutes, scale, and move code from laptop to production without the old headaches. But speed comes at a cost when your container security takes a back seat. Miss a patch, use a default password or pull the wrong image and you open the door to attacks.

IT teams know the pain of exposed secrets, accidental data leaks, workloads hijacked for cryptomining or outages from one compromised container. The stakes are real and one mistake can sideline your business or spark a full-scale incident.

Here’s the good news, strong and consistent Docker security practices can stop these problems before they start. You don’t need a big team or advanced tools as much as you need to employ proven steps that work in fast-moving environments, including infrastructure edge computing.

Good security is often just a matter of attention, pattern recognition and forming habits you can count on, even when projects move quickly. When you know what to look for, protecting your Docker containers becomes part of your everyday workflow, not just another list of tasks to check off.

What is Docker security?

Docker security covers every action you take to keep your containers safe, starting with the images you use, the permissions you grant and the way your apps connect to one another. Containers aren’t sealed boxes; if you rush past security, it’s surprisingly easy to bring in hidden malware, expose private data or let hackers move from one container to another.

You might trust a popular public image or leave an extra port open for testing, and suddenly your system is exposed. These gaps don’t just cause technical headaches — they can lead to real-world business damage, lost customer trust and hours of cleanup after an incident.

Staying ahead means building security into your everyday routine. Scan images, lock down access and pay attention to how your containers communicate. The right habits make attacks less likely and keep your focus on moving forward, not looking over your shoulder.

Common Docker container security vulnerabilities

Most Docker breaches don’t start with sophisticated hacks — they start with small, overlooked details. If you skip a step, rush a deployment or leave a setting unchanged you could be inadvertently creating an opening that attackers notice quickly.

Docker container security vulnerabilities multiply when speed trumps verification. The examples below show how everyday shortcuts during development and deployment create real attack vectors, whether in data centers or at the computing edge.

Malicious or outdated images slip in

Pulling an image straight from a public registry might seem safe, but many carry vulnerabilities or hidden malware by default. Attackers routinely upload altered versions, hoping to get developers to introduce threats into the containers they code on to surpass defenses. Once in production, these images can lead to data loss or system compromise.

Scanning every new or updated image before it’s used closes this gap. Continuous integration (CI) pipelines should flag and block images with known risks, protecting your environment before any workload launches.

Over-exposed networks and open ports

Unnecessary open ports or generous default network settings make lateral movement easy. Even a single forgotten port can be a direct entryway for attackers running automated scans.

Review network rules often. Only the ports required for your application’s core functions should be exposed, and every change needs tracking. This applies to both cloud services and multi-access edge computing. 

Orphaned, unmonitored containers

Test and forgotten containers sometimes continue running for days or weeks, overlooked in daily operations. They’re rarely patched and quickly become vulnerable, especially if security settings are more relaxed during testing.

Regularly audit what’s actually running. Remove any unused containers and make container cleanup part of your routine. Attention here prevents your environment from filling with hidden weak points.

None of these vulnerabilities require advanced skills to fix — just steady routines and focused attention. Each habit you build closes another door and keeps your Docker environment much harder to attack.

Docker container security best practices

Container security comes down to a few reliable routines — nothing flashy, just a series of habits that catch problems before they snowball.

Following Docker best practices security guidelines isn’t just about compliance. It’s about building sustainable protection into your workflow. Here are the Docker security best practices that help teams avoid mistakes and keep their setups out of trouble.

Scan images and containers before they run

Real attacks rarely start with zero-day exploits. They start with a single missed update, like an old library, a vulnerable package, a quietly infected base image. One outdated image lets ransomware take down your app. An unscanned container exposes database credentials to the open internet.

Your first job (a crucial one) is to keep bad code out of your pipeline. Scan every image before it hits production. Most breaches come from known vulnerabilities, like flaws listed in databases for months before anyone acts. The fix? Build scanning checkpoints into every step:

• Scan images on build, before pushing to your registry.
• Block deployments that fail security checks in CI pipelines.
• Run scheduled scans for containers in production.
• React to new security advisories with immediate re-scans.

These steps are quick to automate. They help you catch issues before attackers do. For example, a financial services company avoided a major incident because its CI pipeline flagged a base image with a critical OpenSSL bug. Without that policy, customer data would’ve been exposed.

Don’t rely on hope; use scanning tools to spot trouble the moment it appears. Prioritize vulnerabilities that target authentication, encryption and network modules. These open the fastest paths to compromise. When a scan fails, stop the deployment. Alert your team. Fix the problem right away.

Scanning isn’t a paperwork exercise. Done well, it protects revenue, uptime and customer trust. If you’re not sure your images are clean, are your containers? Better to know before your users (and your attackers) find out first.

Implement least privilege

Every permission you grant is a potential attack path. Excessive rights turn a minor issue into a disaster. If a container can access sensitive directories or internal APIs it doesn’t need, you’ve set the stage for deeper compromise. Attackers count on you to leave doors unlocked.

Most container breaches don’t require deep technical skill; they succeed because someone left a wide-open door. Over-permissioned containers are the easiest targets. Attackers look for containers with root or admin access, broad network rights, or unused system capabilities. They don’t care how it happened; they just walk through.

Here’s how you get it right:

• Identify what each container needs to function.
• Give it access to only those resources. Nothing more.
• Create unique service accounts for each container type.
• Restrict network access to just the required endpoints.
• Remove unnecessary Linux capabilities. Use read-only filesystems when possible.

Put these limits in place at every step: in the Dockerfile, during CI/CD deployment, and at runtime. Set policies that block deployments with excessive privileges. Review permissions whenever something changes. If your monitoring alerts on privilege escalations or unexpected access requests, act immediately. Don’t let drift expose your environment.

Least privilege isn’t a box to check. Make it a living process; tighten permissions with every deployment, cut back further as you learn what’s truly needed, and never assume default rights are safe. The fewer privileges your containers hold, the harder it is for attackers to move, pivot, or cause harm. Small steps here are the difference between a quiet incident and a major breach.

Minimize container size

Every unused library and extra tool in your container is a new way for attackers to breach your boundaries. Large containers hide unnecessary packages — test utilities, compilers, shells — that do nothing for your application but quietly expand your attack surface. One forgotten debugging tool can provide everything an intruder needs to escalate access or run code you never intended.

Smaller containers don’t just start up faster; they’re simpler to secure. Tight images make vulnerability scanning quicker and patching more predictable. When your image holds only the essentials, you know exactly what needs to be updated, and you can cut the turnaround time for security fixes. Teams that cut container size routinely find and remove dozens of outdated packages no one ever needed. Fewer components, fewer places to hide.

Build smaller containers with these steps:

• Start from a minimal base image, not a full operating system.
• Use multi-stage builds to include only runtime dependencies.
• Remove package managers, temp files and build artifacts before shipping.
• Delete documentation, test data and anything not used by your app.
• Audit dependencies regularly and drop what you don’t need.

Consider a software team that started with a 900MB image. By stripping old tools and sticking to a purpose-built base, they cut it to 120MB. After the next CVE dropped, they patched and redeployed within hours. No scrambling through layers of legacy tools, no delays waiting for bloated scans. Their attack surface shrank with every update.

Review your containers every release. Trim where you can. Every package you remove closes another avenue for compromise and keeps your environment lean enough to respond fast when threats emerge.

Manage secrets

Hardcoded secrets turn into breaches. Passwords, API keys and tokens don’t belong in Dockerfiles or images. Leave one behind, and you’ve handed attackers the keys to your systems. You’d be surprised how often credentials end up in public code or inside containers copied from project to project.

Move all secrets outside your images. Use a dedicated secret manager, or your orchestration platform’s built-in tools, to inject credentials only at runtime. Treat hardcoded secrets as critical vulnerabilities. If a database password is embedded anywhere, tear it out immediately.

Here’s how to get it right:

• Store secrets in a secure manager, never in code or images.
• Inject secrets at runtime — environment variables, not files.
• Use short-lived tokens and rotate credentials often.
• Scan every image for accidental secrets before deployment.
• Wipe secrets from build logs and history.

Picture a developer in a hurry checking in a test password to a Dockerfile. Months go by. The code moves to a public repo, and automated scanners pick up the secret almost instantly. It doesn’t take a targeted attack; just a routine sweep. Had this team injected secrets at runtime using a secret manager, those credentials would’ve stayed protected, even as code changed hands.

Scan for secrets every build. Rotate credentials regularly. When you treat secrets like live ammo and never trust a static config, your blast radius gets smaller, and your incident response gets easier.

Continue updating, monitoring and auditing

Unpatched containers don’t sit quietly. They collect vulnerabilities with every passing week. Miss an update, and attackers will find you. Most breaches start with an old base image, an overlooked library, or a critical patch nobody got around to applying. Automated scanners pick up on containers lagging behind, and those become easy targets.

Treat updates and monitoring as daily work, not a quarterly project. Automate image rebuilds on a regular schedule or when a new vulnerability hits the news. Monitor every running container. Watch for network connections you didn’t expect, sudden file changes, or new processes that don’t belong. If you spot something off, investigate before it spreads.

Build these habits into your workflow:

• Rebuild and redeploy containers on a set schedule.
• Subscribe to security advisories and act fast on urgent ones.
• Set up baseline network and behavior profiles for each workload.
• Alert on deviations, whether it’s an outbound IP you don’t recognize or a binary that wasn’t there yesterday.
• Keep a full audit trail: creation, updates, terminations, and changes.

Let’s say a container runs for months without a rebuild. New vulnerabilities appear while it chugs along. Suddenly, your monitoring flags traffic to an unfamiliar IP. Turns out that the container was compromised through an old CVE. With regular patching and container management monitoring, you would have caught the risk and shut it down days earlier.

Don’t let drift build up. Treat every image and workload as a living asset that needs attention. Patch early and often, respond to every alert, and your containers will remain business assets, not attack vectors.

Avoid root mode

Running containers as root hands attackers more power than they should ever have. If someone breaks in, root privileges let them alter system files, install malware, and pivot to the host. A non-root user keeps the damage contained. Attackers can only access files and processes owned by that user.

Make it standard and always specify a non-root user in your Dockerfile. Use the USER instruction to drop privileges before your application starts. Cut back on capabilities. After all, most apps don’t need the ability to mount filesystems, change network settings or access device drivers.

Here’s the right approach:

• Create dedicated users for each container.
• Always switch from root to the correct user before launch.
• Remove capabilities that aren’t required for your app.
• Use read-only mounts whenever possible.
• Never mount the host’s root directory or sensitive paths into a container.

What if a containerized web service runs as root? An attacker exploits a minor file upload flaw, drops a script, and suddenly has access to system folders — possibly the host itself. Run that same service as a non-root user, and an attack stops at the application boundary.

Review user permissions every build. Use root only when you can’t avoid it and document every exception. Containment is your best defense. Restrict privileges, and you limit what any attacker can do.

Easily execute Docker security best practices with SUSE Security

Security starts with the basics. Scan your images for vulnerabilities, store secrets properly and review network settings regularly. Simple automation turns these essentials into reliable routines, not rushed afterthoughts.

When security becomes part of your daily workflow, protection follows naturally. Your environment stays consistent, risks decrease and containers run with confidence. 

Ready to make these Docker security practices stick? Connect with SUSE Security and get your containers locked down right from day one.

Docker security best practices FAQs

Is Docker secure?

Docker is secure if you follow key security best practices, like scanning images, managing secrets and avoiding unnecessary privileges. Containers aren’t immune to attacks, but smart routines greatly reduce your risks and keep workloads protected.

How do you handle secrets in Docker?

Store secrets outside of your images using secret managers or your orchestration tool. Inject them at runtime — never hardcode them in Dockerfiles or images. This ensures credentials stay protected, even if your container is shared or public.

How do you safely stop a Docker container?

Use the docker stop command to gracefully shut down a container. This command gives running processes a chance to finish before the container fully stops, helping you avoid data loss or corruption.