As organizations continue to adopt cloud computing and containerized applications, security has become a top concern. Containers provide numerous benefits like portability and resource efficiency but also introduce new risks that must be addressed. In this comprehensive guide, we will discuss the unique security challenges with containers and how to implement a defense-in-depth strategy to secure your cloud deployments.
Introduction
Containers allow developers to package applications with all their dependencies into standardized units that can run uniformly on any infrastructure. This portability has made containers a cornerstone technology for cloud-native application development.
However, containers have distinctive security needs compared to traditional virtual machines (VMs):
- Containers share the host kernel and resources. A vulnerability in one container could compromise other containers and the underlying host.
- Containers are ephemeral and quickly created, updated, stopped, and destroyed. This dynamic nature makes it difficult to maintain visibility and control.
- Developers focus on rapid iteration and frequently overlook security in the process. Container environments need adequate controls to prevent lapses.
These factors require a new approach to security tailored for containerized environments. In this guide, we will provide best practices to manage container security risks, including:
- Ensuring container host security
- Applying container-specific security controls
- Protecting container data and communications
- Implementing scanning and runtime protections
- Automating security through policy enforcement
- Monitoring container activity and responding to threats
Following these steps will enable you to harness the power of containers securely in the cloud.
Securing the Container Host
The container host is the foundation of any container deployment. It provides the operating environment in which containers run. Securing the host is critical because its vulnerabilities can impact all containers running on it.
Follow these practices to secure your container hosts:
Use Minimal Host OS
Only install essential OS packages needed for hosting containers. Disable unnecessary services, remove extra software, and apply a restrictive firewall policy. Minimizing the host attack surface reduces risks.
Harden the Host OS
Apply security hardening guidelines provided by your OS and cloud vendor. For example, adhere to CIS Benchmarks to harden Linux hosts on AWS or Azure. Harden the kernel, network, and user access following industry standards.
Keep the Host OS Updated
Regularly patch and update the host OS to ensure it has the latest security fixes. Monitor for CVEs that impact the kernel, system libraries, orchestrators, and runtimes. Subscribe to security bulletins from your cloud provider to stay up to date.
Use Host-based Firewalls
Enable host firewalls to restrict network traffic and intra-host communication between containers. For example, use tools like iptables on Linux and screen unwanted access between containers and the host network.
Separate Container Workloads
Do not collocate containers with different trust levels or owned by separate teams on the same host. Provide a degree of isolation by hosting containers from disparate applications on separate infrastructure.
Encrypt Container Data Volumes
Encrypt sensitive container data volumes at rest on the host using LUKS, eCryptfs or other encryption tools. This protects container data if an attacker gains access to the host.
Applying Container Security Controls
In addition to the host, apply security controls designed specifically for containers:
Use Read-Only Containers
Set containers to read-only modes where possible. This prevents malicious or unintended changes from occurring at runtime. Make temporary file systems and volumes writable as needed for only required tasks.
Restrict Container Resources
Set resource limits on CPU, memory, storage, and I/O for containers to prevent resource exhaustion attacks. Assign each container the minimum resources necessary and monitor for spikes.
Define Container User Policies
Do not run containers as root users or with privileged access by default. Create user policies to provide containers with least privilege permissions.
Secure Container Images
Download container images only from trusted repositories. Check digests to validate image integrity. Scan images for vulnerabilities, malware, and compliance with organizational standards before deployment.
Encrypt Container Secrets
Store sensitive data like credentials, keys, and passwords in encrypted secrets. Consume secrets as volumes or environment variables rather than baking into container images.
Scan Containers Frequently
Continuously monitor and scan running containers for vulnerabilities to identify risks in ephemeral environments. Use tools like Twistlock, Aqua, and Anchore to automate container scanning at runtime.
Protecting Container Networks
Containers must communicate with each other, the host, external systems, and users. Proper network security is essential including:
Use Container Firewalls
Implement container firewalls that filter traffic between containers and impose rules for external and internal communications based on allow listing.
Encrypt Container Networks
Encrypt container network traffic, especially across untrusted networks. Utilize IPSec, TLS, SSL, or VPNs to secure communications in transit.
Segment Container Networks
Logically segment containers into distinct security groups (e.g. front-end, back-end, database, etc). Only allow permitted traffic between these groups.
Limit Network Exposure
Only expose network ports required for a container’s legitimate external communication. Avoid exposing unnecessary ports or admin interfaces externally.
Integrate with Host Networks
Manage container networking through the host rather than directly bridging containers. This allows enforcing network policies through the host firewall.
Scan for Misconfigurations
Continuously scan container networks to detect misconfigured policies, unnecessary exposures, vulnerabilities in applications and services, suspicious outgoing traffic, and other risks.
Implementing Runtime Protections
To provide ongoing protection for containers at runtime:
Deploy Web Application Firewalls
Deploy WAFs on container ingress to protect against OWASP Top 10 threats like injection attacks, cross-site scripting, and input validation issues.
Enable DDoS Protection
Enable volumetric DDoS protection provided by cloud vendors or third parties to safeguard container workloads from large scale attacks.
Mask Sensitive Data
Mask sensitive data like credit cards and social security numbers displayed in logs, analytics, and dashboards. This reduces risk if container logs and data are compromised.
Mask Containers
Do not expose actual container names, hosts, tags, or other identifiers. Use randomized IDs to obscure targeting of specific containers by attackers.
Continuously Monitor Containers
Collect and analyze container logs in real-time to identify signs of compromise like spikes in errors, policy violations, suspicious network connections, anomalous user behavior, and known attack patterns.
Scan Container Registries
Continuously scan container registries for vulnerabilities in cached container images, malicious or compromised images, and enforcement of security policies.
Use Anomaly Detection
Apply machine learning techniques to detect subtle anomalies that could indicate threats – such as unauthorized changes to configurations or network micro-segmentation policies.
Enforcing Security via Policy
A centralized policy engine enables automation and consistency of security controls across ephemeral containers. Major capabilities include:
Treat Containers as Cattle
Automate container security versus manual controls. Destroy and rebuild compromised containers based on policy versus attempting remediation.
Embed Policies in Code
Embed security policies as code in CI/CD pipelines and configuration management (e.g. Kubernetes YAML) to enforce consistent policy.
Integrate with Admission Control
Integrate policy enforcement with Kubernetes admission webhook controllers to validate configurations pre-deployment against security standards.
Policy-Based Network Control
Dynamically isolate, segment, and encrypt container traffic based on policy versus static network rules. Add zero-trust software-defined perimeters.
Policy-Driven Encryption
Apply encryption dynamically based on contextual policy factors like container type, sensitivity of data, registry source, and user context.
Automate Responses
Automatically trigger policy-based responses to threats and anomalies – such as isolating impacted containers, shutting down ingress/egress, killing containers, and alerting security teams.
Monitoring Container Security
Observability into container activity is foundational for security monitoring, threat detection, compliance, and auditing including:
Monitor Host and Containers
Centrally monitor logs, metrics, events, network traffic, system calls, and files changes for hosts and containers. Feed data into SIEMs and analytics.
Implement Audit Logging
Log all administrative user actions and events related to containers, hosts, orchestrators, registries, and environments. Do not allow container modifications without audit records.
Detect Compromised Containers
Analyze container behavior to detect compromised instances being used in cryptomining, data exfiltration, botnets, and other malicious activities.
Detect Privilege Escalation
Monitor and analyze process and user activity within containers to detect privilege escalation, lateral movement, and stresses that could indicate a compromised container.
Monitor User Access
Monitor and control administrative access to container environments. Allow only authorized user access and integrate with centralized identity systems like LDAP or OAUTH.
Retain Audit Records
Retain audit data to satisfy compliance requirements and for security forensic analysis according to policies – such as 90 days online, 1 year archive.
Monitor Compliance Posture
Continuously assess containers against compliance standards and best practices, such as CIS Docker Benchmark, PCI-DSS, HIPAA, and internal security policies.
By taking advantage of native cloud security tools and purpose-built third party solutions, organizations can gain comprehensive visibility and control over their container environments.
Conclusion
Containers introduce major benefits but also new security risks that organizations must mitigate. The ephemeral and dynamic nature of containers requires securing the entire container lifecycle – from image creation to runtime.
This guide outlines a defense-in-depth approach including:
- Hardening container hosts
- Applying granular controls to containers
- Protecting container data and communications
- Detecting threats with runtime monitoring
- Enforcing security through policy automation
- Maintaining visibility for compliance and forensics
Following cloud-native security best practices enables you to securely reap the advantages of containers. With proper vigilance and defense-in-depth controls, organizations can confidently accelerate cloud adoption and securely run innovative containerized workloads.
