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Multi-tenant software-as-a-service (SaaS) systems serve several separate groups of users (tenants) from a single physical platform. Each tenant's data is logically isolated, meaning that they only see their own resources, but tenants generally share the same underlying infrastructure.
Multi-tenancy lets you optimize system performance, reduce operating costs, and simplify deployment processes. However, it poses unique security and privacy challenges. Robust tenant isolation controls are crucial to prevent data leaks and stop attacks against one tenant from impacting its neighbors.
In this guide, we explore 10 best practices for securing multi-tenant SaaS platforms. These actionable strategies will let you build scalable SaaS systems that protect your organization and your customers.
What is multi-tenant SaaS and what risks does it bring?
Multi-tenancy is the sharing of physical resources between several logical consumers, with each tenant using the same infrastructure, service deployments, and database environments.
The concern with this approach is that improperly isolated tenants could be exposed to each other's data. In advanced scenarios, multi-tenancy may be implemented with a degree of physical separation to provide greater isolation, but these systems aren’t without risk either.
Common multi-tenant SaaS threats include:
- Data leakage between tenants: Misconfigurations, vulnerabilities, and weak isolation controls can allow data to move across tenant boundaries, posing privacy, compliance, and regulatory risks.
- Noisy neighbor problems: Activity peaks in one tenant can limit the resources available to others. Not only does this cause performance problems, but it can also exacerbate denial of service attacks.
- Authentication issues: Teams must carefully implement tenant-level authentication controls to ensure access requests always target the correct tenant.
- Difficulty in monitoring tenant activity: Per-tenant monitoring controls must cut across shared infrastructure while preserving strict tenant isolation. Teams may skip this process due to fears that misconfigured observability platforms will leak tenant data, but skipping monitoring may let malicious activity persist unnoticed.
Securing your multi-tenant SaaS environments requires taking steps to mitigate all of the above concerns.
10 security best practices for multi-tenant SaaS isolation
Now that we've discussed why multi-tenant SaaS security is so important, let's take a look at 10 ways to address risks and protect your environment.
1. Enable row-level encryption using per-tenant keys
Encrypting records at the row-level is one of the most basic mechanisms for keeping tenanted data secure. It lets you apply a different encryption key to each tenant's records; this way, even when tables contain data from multiple tenants, an attacker with one tenant's key can't steal data from the others. Because each session must be initialized with a specific tenant’s key, this technique also prevents application bugs from retrieving data that belongs to neighboring tenants.
An added plus to row-level encryption is that it lets you implement bring your own key (BYOK) encryption options. When tenants configure their own encryption keys, they feel reassured that only they can access their data. BYOK also means tenants can back up encrypted data to their own infrastructure, then decrypt the data later when it’s needed. This keeps backups protected during transit.
2. Implement resilient authentication and access controls
Multi-tenant systems are only as secure as your authentication layer. Access controls must be properly configured to identify tenanted users, then restrict them to their own data.
Building multi-tenant auth systems can be complex. It's often safer to use single sign-on (SSO), OpenID Connect (OIDC), and security assertion markup language (SAML) to let tenants connect their existing external identity providers and IAM platforms. Tenanted users can then authenticate themselves through platforms such as AWS, Google, GitHub, and Slack.
This reduces implementation complexity while letting the tenant apply their internal standards for role-based access control (RBAC), multi-factor authentication (MFA), and audit controls.
3. Host critical tenants on dedicated infrastructure
Not all tenants necessarily have the same performance and security needs. For instance, some customers may request that their data be kept completely separate from other tenants to meet specific regulatory requirements.
In these scenarios, you may need to provision dedicated infrastructure for affected tenants. Instead of operating all tenants from a single instance, selective use of multiple instances can help you better meet the needs of high-value but demanding customers, without making this the norm for everyone.
This model is an increasingly common option from large-scale SaaS providers. For example, GitLab now provides a GitLab Dedicated service that gives customers a private cloud-hosted instance, running on isolated infrastructure.
4. Separate tenants at the network level using network policies, VLANs, and SDNs
Achieving full isolation in multi-tenant SaaS systems requires tenants to be separated at the network level. While this won't be appropriate for every environment, it provides additional safeguards when you're dealing with sensitive data or complex regulatory requirements.
Network controls such as virtual local area networks (VLANs) and software-defined networking (SDN) policies enable you to enforce this network-level isolation.
For instance, assigning each tenant its own VLAN stops tenanted traffic from crossing network boundaries to reach infrastructure components owned by other tenants. Similarly, SDN rules and network policies let you control exactly which components can communicate with each other in virtualized environments like Kubernetes clusters.
5. Use database sharding to balance tenant isolation and performance requirements
Database sharding involves splitting a database table's records into multiple partitions. The partitions all have the same table structure, but each one stores a different portion of the data. This can improve performance for large tables by letting you horizontally scale the table’s data across multiple compute nodes.
Multi-tenancy is one of the many use cases for sharding. Partitioning large tables of tenanted data lets you separate the records belonging to each tenant. The data can then be isolated on different compute nodes to improve safety and resiliency.
With sharded tables, problems affecting one tenant are less likely to impact other tenants. Tenants also benefit from more consistent performance, as the database only needs to search the records within their specific shard.
6. Track tenant activity with context tags in audit logs
Unless you're tracking tenant activity, you've no way of knowing whether you're meeting your isolation and privacy requirements. To provide this crucial context, log messages and request traces should be tagged with the tenant who generated them.
Including tenant context in your logs allows you to answer questions about who's accessing data, when, and from where. It lets you effectively audit your multi-tenant infrastructure to assess suspicious activity, investigate breaches, and solve tenant performance problems.
7. Periodically audit stored tenant data for inter-tenant leaks and cross-over
Don't assume your multi-tenant isolation systems are working properly. New changes, misconfigurations, and vulnerabilities may cause inter-tenant breaches to occur. The fallout from these incidents can be catastrophic if they’re not caught early: Exposing private tenanted data to other customers will usually carry severe reputational and regulatory penalties.
Defend against this threat by regularly running automated audits capable of exposing data anomalies—before an issue is noticed by users. For instance, scans could identify that records for one tenant are being created from IP addresses or locations known to belong to another tenant.
8. Implement robust tenant activity monitoring to detect targeted attacks
The risks of multi-tenancy aren't confined to platform-level isolation issues. Individual tenants may be subject to targeted attacks, whether from adjacent tenants or outside your infrastructure. Systems need to be designed so that a breach of one user account can't snowball into a multi-customer incident.
Robust automated monitoring and response solutions are the best mitigation. Using cloud security platforms to spot anomalous activity in real time lets you stay ahead of penetration attempts.
If you detect a live attack against one tenant, then your platform should take defensive action to keep other tenants safe. For instance, you could rotate each tenant's encryption keys or temporarily isolate dedicated infrastructure used by the affected tenant.
9. Prepare incident response runbooks for dealing with tenant breaches
Multi-tenant systems are complex, making dealing with incidents stressful. Catastrophes such as inter-tenant leaks need to be handled swiftly, but your response should still follow a structured process. This will help you avoid making mistakes that could compound the original problem.
Maintaining clear incident response (IR) runbooks ensures team members have a reference available after disaster strikes. Runbooks should succinctly describe your system's architecture, explain the potential tenant-level effects of different attacks, and provide clear steps for how to isolate critical components. This will enable team members to recover service quickly without risking data integrity or tenant isolation issues.
Automating key recovery steps, such as providing a one-click action to restore an individual tenant's backups, also plays an essential role in building recovery processes that are both fast and safe.
10. Implement tenant-level lockouts and kill switches to halt malicious activity
If a tenant is affected by malicious activity, then the ability to lock that customer out of your system can help stop the attack from spreading to other tenants. Such lockout mechanisms and kill switches let you trigger targeted firebreaks to protect the rest of your platform.
At its simplest, a kill switch could simply mean disabling a tenant so its users can no longer authenticate with your SaaS. This is an effective way to quarantine tenants when user credentials may have been stolen.
More sophisticated lockout systems defend against unknown external adversaries by filtering at the network level. For instance, you could enforce an infrastructure-level policy to temporarily reject traffic targeting a tenant's endpoints. Similarly, the ability to filter out traffic from particular IP addresses, regions, or origin networks can let you thwart attackers without disrupting service for other tenants.
RapidScale: Your trusted partner for building multi-tenant SaaS in the cloud
Multi-tenant SaaS systems allow you to serve multiple customers, clients, or partners from one deployment. The model improves operating efficiency by letting you share resources between tenants. But it's crucial to bake in strong security protections that ensure each tenant's data stays properly isolated.
Designing your own multi-tenant SaaS platform? At RapidScale, we specialize in expanding your cloud capabilities.
Our managed services for public, private, and hybrid clouds let you unlock innovation to advance your business. We'll guide you through planning your multi-tenant security requirements, then implement dependable tools that protect your operations.
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