While Hamlet asked the existential question “to be or not to be,” most security teams ask an equally esoteric question that ultimately defines their ability to manage alerting and detection: “to deploy on-prem or in the cloud?”
When adopting a security information and event management (SIEM) solution, organizations must make a foundational decision around whether to deploy the solution on-premises or in the cloud. While cloud offers benefits like scalability and cost efficiency, on-prem deployments may work better for specific environments, like those containing operational technology (OT).
By understanding the similarities and differences between cloud and on-premises SIEM deployments, organizations can make the decision that fits their needs best.
What is SIEM deployment?
The SIEM deployment refers to the architectural model that dictates:
- Where the organization installs the software.
- How the organization stores and processes the information.
- Who manages the underlying infrastructure.
On-Prem Deployment
An on-prem SIEM deployment takes the traditional approach to log management and security analytics, where the organization uses its data centers to host the solution after purchasing the software license. The organization is responsible for the following:
- Hardware procurement and maintenance, including log data storage and servers for processing.
- Installation, configuration, and management, including patching vulnerabilities and scaling capacity.
With this model, organizations have complete, direct control over security data and the infrastructure.
Cloud-Based SIEM
A third-party vendor hosts and manages a cloud-based SIEM, typically using the Software-as-a-Service (SaaS) model. The organization accesses the platform through a web-based interface, with log data sent to the vendor’s cloud environment for storage and processing. With the vendor responsible for all infrastructure, maintenance, and software updates, the organization can define the SIEM as an operating expense, eliminating the large up-front capital investments.
As the SaaS model evolves, more vendors offer cloud-native SIEMs with integration and scalability functionalities that respond to cloud environments. According to experts, changes in data volumes can arise from:
- Changes to log settings
- Upgrades
- Troubleshooting
- Misconfigurations
A cloud-based SIEM may help respond to these concerns.
Comparing On-Prem vs Cloud SIEM Deployments
When choosing between on-prem and cloud-based solutions, organizations should consider the environments they need to secure and how the technology enables them to detect threats and respond to incidents.
Use Cases
When seeking to deploy a SIEM, organizations should consider the environments they need to protect and how the different technologies respond to those needs.
An on-prem SIEM enables organizations to store and process security telemetry while complying with strict regulatory or data sovereignty requirements. An on-prem SIEM responds to use cases like:
- Environments in heavily regulated industries, like government, defense, and some financial services sectors.
- Requirements for maintaining absolute control over highly sensitive log data.
- Organizations with minimal cloud presence and heavy investment in legacy on-prem infrastructure that require deep, localized integration.
A cloud SIEM enables organizations to manage the dynamic security data that modern IT environments generate. A cloud-based solution respond to use cases like:
- Distributed or remote workforces that take a cloud-first approach to enterprise IT.
- Fluctuating data volumes from sources like SaaS applications and cloud infrastructure.
- Offloading infrastructure management.
- Security teams that want to focus their limited resources on higher-value threat detection and incident response tasks.
Infrastructure Requirements
The fundamental difference between the two deployments lies in their infrastructure demands.
An on-prem SIEM requires significant initial and ongoing investment that can include:
- Physical hardware, like servers, storage arrays, and networking equipment.
- Considerations for power, cooling, physical data center security.
- Hardware lifecycle management, including vulnerability management.
With a cloud-based SIEM, the vendor maintains the infrastructure leaving the organization responsible for the following:
- Reliable, high-bandwidth connectivity to ingest log data.
- Cloud storage for retaining and querying large data volumes, like adopting a security data lake.
- API and agents to support ingesting data from security solutions and enterprise IT.
Key Features
While both deployments offer similar functionalities, they have different primary features that respond to their different use cases.
An on-prem SIEM has the following key features:
- Customizable data ingestion and parsing with deep ability to tune collectors, parsers, and correlation rules.
- Lower latency for on-prem network events.
- Integrations with proprietary or legacy systems.
- Function in isolated or high-security environments with no internet access.
However, to deploy an on-prem SIEM, organizations often need to have staff with the appropriate experience.
Cloud SIEM platforms offer the following key features:
- Rapid deployment with no infrastructure to maintain.
- Threat intelligence and analytics that continuously update and integrate with artificial intelligence (AI) and machine learning (ML) models.
- Correlation access hybrid environments, including on-prem, cloud, and SaaS data sources.
- Scalability and flexibility to handle log volume spikes without hardware constraints.
Cost
The two deployments have different cost considerations, especially when reviewing how the organization budgets for and reports the costs.
Organizations that deploy an on-premises SIEM must consider:
- Capital Expenditures (CapEx): Hardware (servers, storage), perpetual software licenses, and initial implementation fees.
- Operational Expenditures (OpEx): Salaries for dedicated IT and security professionals, annual maintenance and support contracts, power, cooling, and data center space.
With a cloud SIEM, the total cost of ownership (TCO) is typically OpEx-based as follows:
- Subscription Fees: Based on data volume (gigabytes per day), event rate (events per second), or number of users.
- Variable Costs: Additional charges for data retention beyond a standard period, advanced analytics features, or professional services.
5 Considerations when Choosing a SIEM
For many organizations, choosing a SIEM is an either/or decision. However, in some cases, organizations may want a hybrid on-premises and cloud-based SIEM deployment. When making these decisions, organizations should consider the following capabilities.
Scalability and Performance
Often a cloud or hybrid deployment enables organizations to scale their SIEM more easily. Some questions that organizations should ask themselves include:
- How much data will the SIEM need to ingest?
- How quickly can the SIEM retrieve historical data?
- What is the indexing performance?
- How many additional resources, like disks or servers, will be needed?
Data Retention, Archiving, and Storage
Depending on an organization’s compliance requirements, retaining and storing log data may become a financial and operational concern. Some questions that organizations should ask themselves include:
- How long must logs be retained?
- What logs do security teams need quick access to?
- What historical data can be archived?
- How can the solution help balance storage cost against retrieval speed?
- Can the staff manage disk space, index rotation, and archiving?
Operational Overhead and Support
While on-premises and cloud-based SIEMs have different requirements, they both require organizations to have the appropriate infrastructure and staff to manage and maintain the solutions. Some questions that organizations should ask themselves include:
- Who will be responsible for infrastructure, updates, security patches, scaling, disaster recovery, and backup with an on-prem solution?
- Does current staff have the appropriate experience for managing either deployment model?
- What are a cloud-based SIEM vendor’s uptime guarantees and compliance certifications?
Control, Access, and Customization
While the organization controls an on-prem SIEM’s underlying infrastructure, both deployments require configuration and customization to ensure they respond to the defined security risk and use cases. Some questions that organizations should ask themselves include:
- Have staff appropriately configured and implemented underlying servers, file systems, SSH access, and any nodes?
- Are system-level controls restricted for the cloud deployment, including preventing SSH access to server nodes, limiting index rotation, ensuring appropriate timeout, and restricting user access according to the principle of least privilege?
- Can the security team customize pipelines, inputs/outputs, collectors, and legacy components?
- Are there different features available or restricted in cloud versus on-prem deployments that must be considered?
Hybrid Deployment, Forwarding Capabilities, and Integrations
For some organizations, deploying both an on-prem and cloud-based SIEM makes the most sense, especially if they have sensitive air-gapped environments, like ones managing OT. in this case, some questions that those organizations should ask themselves include:
- What log forwarding, clustering, and replication capabilities are necessary?
- Can the solution support forwarding logs from on-prem to the cloud?
- Does the solution integrate with the required security technologies, like identity systems, alerting, compliance tools, and external log sources or applications?
Graylog Security: The Flexible Solution to the Cloud vs. On-Prem SIEM Question
Graylog Security offers organizations the freedom to choose the SIEM deployment model that best fits their operational, compliance, and scalability needs. Whether deployed on-premises, in the cloud, or as a hybrid solution, Graylog delivers the same powerful analytics, threat detection, and log management capabilities.
Organizations that need complete control over data, configurations, and retention can deploy on-prem, while those seeking scalability, reduced overhead, and faster time-to-value can leverage Graylog Cloud.
For teams operating in mixed environments, hybrid options provide seamless data forwarding and centralized visibility across both domains. With Graylog’s unified architecture and intuitive design, security teams gain the flexibility to evolve their SIEM strategy as infrastructure, compliance, and business demands change.
