☁️ CLOUD SECURITY FUNDAMENTALS • CISO GUIDE

Cloud Security 101: Your Step-by-Step Guide to Understanding and Applying the Shared Responsibility Model

By CyberDudeBivash • October 07, 2025 • Strategic Pillar Post

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Disclosure: This is a foundational guide for IT and security leaders. It contains affiliate links to relevant enterprise security solutions. Your support helps fund our independent research.

Guide: Table of Contents

Chapter 1: The #1 Cloud Security Mistake You’re Probably Making

The single most dangerous misconception in cloud computing is the belief that “the cloud is secure.” This leads to a catastrophic mistake: assuming that the cloud provider (AWS, Azure, GCP) is responsible for all of your security. They are not. A fundamental misunderstanding of your role in the security partnership is the root cause of the vast majority of cloud data breaches. The framework that governs this partnership is called the **Shared Responsibility Model**, and mastering it is non-negotiable for any organization operating in the cloud.

Chapter 2: Defining the Model — IaaS vs. PaaS vs. SaaS

The core principle is simple:

The cloud provider is responsible for security **OF** the cloud (the physical data centers, the servers, the network fabric).
You, the customer, are responsible for security **IN** the cloud (your data, your configurations, your user access).

The balance of who does what depends entirely on the service model you choose.

Infrastructure as a Service (IaaS) – e.g., EC2, Azure VM

You are renting an empty, unfurnished house. The provider secures the foundation and walls, but **YOU** are responsible for the operating system and everything on top of it: patching the OS, configuring the host-based firewall, securing your application code, and managing all data and user access.

Platform as a Service (PaaS) – e.g., Heroku, Azure App Service

You are renting a furnished house. The provider manages the OS, the patching, and the underlying runtime (like the database engine). **YOU** are responsible for securing your application code, managing your data, and controlling who has access to it.

Software as a Service (SaaS) – e.g., Microsoft 365, Salesforce

You are staying in a hotel room. The provider manages almost everything. But **YOU** are still responsible for your data, for managing which users have access, and for not falling for a phishing attack. The hotel locks the front door, but you are still responsible for locking your own room door.

Chapter 3: A Practical Checklist for YOUR Responsibilities

Regardless of the model, the customer is ALWAYS responsible for these five key areas:

Identity & Access Management (IAM):** Configuring users, roles, and permissions. Enforcing the Principle of Least Privilege. Mandating strong MFA.
**Data Security:** Classifying your data, encrypting it (both at rest and in transit), and managing data loss prevention (DLP) policies.
**Application Security:** Securing the code you write and deploy in the cloud.
**Network & Configuration Management:** Correctly configuring your security groups, virtual private clouds (VPCs), and other cloud service settings.
**Endpoint & Workload Security:** Patching and protecting the virtual machines, containers, and serverless functions that you run in the cloud.

Manage Your Side of the Bargain: A Cloud Security Posture Management (CSPM) and Cloud Workload Protection Platform (CWPP) are essential tools for managing your responsibilities. **Kaspersky Hybrid Cloud Security** provides this unified visibility, helping you find misconfigurations and protect your workloads.

Chapter 4: The Strategic Takeaway — You Can Outsource Infrastructure, Not Risk

For every CISO and business leader, the Shared Responsibility Model is a framework for accountability. Moving to the cloud allows you to outsource the operational tasks of racking servers and managing hypervisors, but you can **never outsource the ultimate risk or accountability** for protecting your company’s data.

A data breach caused by a misconfigured S3 bucket or a weak password is not the cloud provider’s fault; it is yours. A mature cloud strategy requires a deep understanding of this model and a robust cloud security program to manage your side of the bargain. Your data, your rules, your responsibility.

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About the Author

CyberDudeBivash is a cybersecurity strategist with 15+ years in cloud security architecture, risk management, and governance, advising CISOs across APAC. [Last Updated: October 07, 2025]

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