Defense in depth is a strategy that employs a series of mechanisms to slow the advance of an attack aimed at acquiring unauthorized access to information. Each layer provides protection so that if one layer is breached, a subsequent layer is already in place to prevent further exposure. Microsoft applies a layered approach to security, both in physical data centers and across Azure services. The objective of defense in depth is to protect and prevent information from being stolen by individuals who are not authorized to access it.
Defense in depth can be visualized as a set of concentric rings, with the data to be secured at the center. Each ring adds an additional layer of security around the data. This approach removes reliance on any single layer of protection and acts to slow down an attack and provide alert telemetry that can be acted upon, either automatically or manually. Let’s take a look at each of the layers.
In almost all cases, attackers are after data:
· Stored in a database
· Stored on disk inside virtual machines
· Stored on a SaaS application such as Office 365
· Stored in cloud storage
It’s the responsibility of those storing and controlling access to data to ensure that it’s properly secured. Often, there are regulatory requirements that dictate the controls and processes that must be in place to ensure the confidentiality, integrity, and availability of the data.
· Ensure applications are secure and free of vulnerabilities.
· Store sensitive application secrets in a secure storage medium.
· Make security a design requirement for all application development.
Integrating security into the application development life cycle will help reduce the number of vulnerabilities introduced in code. We encourage all development teams to ensure their applications are secure by default, and that they’re making security requirements non-negotiable.
· Secure access to virtual machines.
· Implement endpoint protection and keep systems patched and current.
Malware, unpatched systems, and improperly secured systems open your environment to attacks. The focus in this layer is on making sure your compute resources are secure, and that you have the proper controls in place to minimize security issues.
· Limit communication between resources.
· Deny by default.
· Restrict inbound internet access and limit outbound, where appropriate.
· Implement secure connectivity to on-premises networks.
At this layer, the focus is on limiting the network connectivity across all your resources to allow only what is required. By limiting this communication, you reduce the risk of lateral movement throughout your network.
· Use distributed denial of service (DDoS) protection to filter large-scale attacks before they can cause a denial of service for end users.
· Use perimeter firewalls to identify and alert on malicious attacks against your network.
At the network perimeter, it’s about protecting from network-based attacks against your resources. Identifying these attacks, eliminating their impact, and alerting you when they happen are important ways to keep your network secure.
Identity and access
· Control access to infrastructure and change control.
· Use single sign-on and multi-factor authentication.
· Audit events and changes.
The identity and access layer is all about ensuring identities are secure, access granted is only what is needed, and changes are logged.
· Physical building security and controlling access to computing hardware within the data center is the first line of defense.
With physical security, the intent is to provide physical safeguards against access to assets. This ensures that other layers can’t be bypassed, and loss or theft is handled appropriately
You can integrate Security Center into your workflows and use it in many ways. Here are two examples.
1. Use Security Center for incident response.
Many organizations learn how to respond to security incidents only after suffering an attack. To reduce costs and damage, it’s important to have an incident response plan in place before an attack occurs. You can use Azure Security Center in different stages of an incident response.
You can use Security Center during the detect, assess, and diagnose stages. Here are examples of how Security Center can be useful during the three initial incident response stages:
o Detect. Review the first indication of an event investigation. For example, you can use the Security Center dashboard to review the initial verification that a high-priority security alert was raised.
o Assess. Perform the initial assessment to obtain more information about the suspicious activity. For example, obtain more information about the security alert.
o Diagnose. Conduct a technical investigation and identify containment, mitigation, and workaround strategies. For example, follow the remediation steps described by Security Center in that particular security alert.
2. Use Security Center recommendations to enhance security.
You can reduce the chances of a significant security event by configuring a security policy, and then implementing the recommendations provided by Azure Security Center.
o A security policy defines the set of controls that are recommended for resources within that specified subscription or resource group. In Security Center, you define policies according to your company’s security requirements.
o Security Center analyzes the security state of your Azure resources. When Security Center identifies potential security vulnerabilities, it creates recommendations based on the controls set in the security policy. The recommendations guide you through the process of configuring the needed security controls. For example, if you have workloads that do not require the Azure SQL Database Transparent Data Encryption (TDE) policy, turn off the policy at the subscription level and enable it only in the resources groups where SQL TDE is required.