SaaS, IaaS, and PaaS are the three core cloud service models. They differ in how much of the work the provider takes on and how much stays with the customer. IaaS (Infrastructure as a Service) delivers just the infrastructure: compute, storage, and networking as virtual machines. PaaS (Platform as a Service) adds a ready-made environment for running applications and developer tooling, and takes over operating-system and server management. SaaS (Software as a Service) is a finished application in the browser — the provider handles almost everything except the customer’s data and user accounts.
What is the difference between SaaS, IaaS, and PaaS?
All three models sit on the same layered IT setup. The only thing that changes is where the line falls between what the provider manages and what stays with the customer. From bottom to top, the layers are: networking, storage, servers, virtualization, operating system, middleware, runtime, data, and the application.
- IaaS — the provider manages the hardware and virtualization (networking, storage, servers, hypervisor). Everything else is the customer’s: operating system, middleware, runtime, applications, and data, plus patching, configuration, and access control.
- PaaS — the provider additionally takes on the operating system, middleware, and runtime. The customer is left with only their own code and data.
- SaaS — the provider manages everything, including the application itself. The customer mainly controls the data they enter, accounts and permissions, and settings within their own account (tenant).
The rule is simple: the higher up you go (IaaS → PaaS → SaaS), the less you manage and the less control you keep, but the fewer duties you carry.
What is IaaS and what is it used for?
IaaS is virtual compute resources on demand, billed for what you actually use (pay-as-you-go). The customer gets virtual machines, disks, networks, and addressing, then installs their own operating system and all software on top. Of the three models, it gives the most freedom and control.
- Typical uses: development and test environments, application hosting, moving existing systems to the cloud (lift-and-shift), data warehouses, backup and disaster recovery, and workloads with variable demand.
- Examples: Amazon EC2, Google Compute Engine, Microsoft Azure Virtual Machines, DigitalOcean Droplets.
What is PaaS and what is it used for?
PaaS is a ready-made platform for building, testing, and running applications. Developers deal only with code and data, while the provider handles the rest: scaling, OS patching, and platform components (databases, message queues, CI/CD tooling).
- Typical uses: rapid web application, API, and microservice development, CI/CD environments, and projects with multiple developers working on the same codebase.
- Examples: Heroku, Google App Engine, AWS Elastic Beanstalk, Red Hat OpenShift, Azure App Service.
A specialized subtype is FaaS (Function as a Service), the serverless model. The provider runs individual functions in response to events and scales them automatically (e.g., AWS Lambda, Azure Functions, Google Cloud Functions).
What is SaaS and what is it used for?
SaaS is a finished application available over the internet, usually on a subscription, accessed through a browser or an API. The provider handles hosting, updates, availability, and most security, while the customer simply uses it — with nothing to install or maintain.
- Typical uses: email, office suites and collaboration, CRM, ERP, accounting, HR tools, messaging, and ticketing systems.
- Examples: Microsoft 365, Google Workspace, Salesforce, Dropbox, Slack, Zoom.
Who is responsible for what in each model (shared responsibility)?
The shared responsibility model spells out who — provider or customer — secures which layer. The general rule: the provider is responsible for “security of the cloud” (hardware, data centers, hypervisor), and the customer for “security in the cloud” — whatever they deploy and configure themselves.
- IaaS — the provider secures the hardware and virtualization. The customer carries the most: OS hardening, patching, virtual network and security-group settings, encryption, identity management (IAM), applications, data, and monitoring.
- PaaS — the provider secures the platform (operating system, runtime, components). The customer is responsible for their own code (its vulnerabilities and dependencies), correct configuration of platform services, accounts, and data.
- SaaS — the provider is responsible for most layers, including the application. The customer keeps control over accounts and access (accounts, MFA, roles), their tenant settings, data classification, and endpoint devices. The most common cause of SaaS incidents is exactly this: customer-side misconfiguration and excessive permissions, not flaws in the application itself.
The takeaway is one: responsibility for identity, access, and data stays with the customer in every model — including SaaS.
Why do cloud models matter for security and monitoring?
Each model affects visibility differently — that is, how much data about what’s happening (telemetry) you actually get. And that decides how much a SOC team and NDR or SIEM tooling can detect.
- IaaS gives the most insight: the customer sees OS logs, network traffic (e.g., VPC Flow Logs, packet mirroring), API-level hypervisor logs, and host telemetry. That allows analyzing internal (east-west) traffic and spotting network anomalies.
- PaaS limits insight to the application and platform layer. The customer usually can’t see network packets or the operating system, so they rely on application logs, platform logs, and provider-exposed metrics.
- SaaS gives the least: monitoring relies on audit logs and API events exposed by the provider (e.g., logins, permission changes, file sharing), often collected by CASB or SSPM tools. With no view into the network or system, detection depends entirely on how good and complete the provider’s logs are.
In short: the higher up the model, the less native network telemetry you own — this is often called loss of visibility. That’s why hybrid and multi-cloud environments require deliberately combining sources: network flows from IaaS, platform logs from PaaS, and audit logs from SaaS, to see the whole picture.
Learn more
- Cloud Security Posture Management (CSPM) — CSPM helps secure SaaS, IaaS, and PaaS cloud configurations.
- On-premise / Cloud / Hybrid — It shows where SaaS, IaaS, and PaaS are deployed: on-premise, cloud, or hybrid.
- Microsegmentation — Microsegmentation limits lateral movement in IaaS and PaaS environments, and supports SaaS isolation.
