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OS X v10.5.1 and later include an application firewall you can use to control connections on a per-application basis (rather than a per-port basis). This makes it easier to gain the benefits of firewall protection, and helps prevent undesirable apps from taking control of network ports open for legitimate apps.
Use these steps to enable the application firewall:
Make sure you have updated to Mac OS X v10.5.1 or later. Then, use these steps to enable the application firewall:
Selecting the option to 'Block all incoming connections' prevents all sharing services, such as File Sharing and Screen Sharing from receiving incoming connections. The system services that are still allowed to receive incoming connections are:
To use sharing services, make sure 'Block all incoming connections' is deselected.
To allow a specific app to receive incoming connections, add it using Firewall Options:
You can also remove any apps listed here that you no longer want to allow by clicking the Remove App (-) button.
Applications that are signed by a valid certificate authority are automatically added to the list of allowed apps, rather than prompting the user to authorize them. Apps included in OS X are signed by Apple and are allowed to receive incoming connections when this setting is enabled. For example, since iTunes is already signed by Apple, it is automatically allowed to receive incoming connections through the firewall.
If you run an unsigned app that is not listed in the firewall list, a dialog appears with options to Allow or Deny connections for the app. If you choose Allow, OS X signs the application and automatically adds it to the firewall list. If you choose Deny, OS X adds it to the list but denies incoming connections intended for this app.
If you want to deny a digitally signed application, you should first add it to the list and then explicitly deny it.
Some apps check their own integrity when they are opened without using code signing. If the firewall recognizes such an app it doesn't sign it. Instead, it the 'Allow or Deny' dialog appears every time the app is opened. This can be avoided by upgrading to a version of the app that is signed by its developer.
Enabling stealth mode prevents the computer from responding to probing requests. The computer still answers incoming requests for authorized apps. Unexpected requests, such as ICMP (ping) are ignored.
The application firewall is designed to work with Internet protocols most commonly used by applications – TCP and UDP. Firewall settings do not affect AppleTalk connections. The firewall may be set to block incoming ICMP 'pings' by enabling Stealth Mode in Advanced Settings. Earlier ipfw technology is still accessible from the command line (in Terminal) and the application firewall does not overrule any rules set using ipfw. If ipfw blocks an incoming packet, the application firewall does not process it.-->
Azure Active Directory (Azure AD) offers many capabilities for protecting users, apps, and data in the cloud and on-premises. In particular, the Azure AD Application Proxy feature can be implemented by IT professionals who want to publish on-premises web applications externally. Remote users who need access to internal apps can then access them in a secure manner.
The ability to securely access internal apps from outside your network becomes even more critical in the modern workplace. With scenarios such as BYOD (Bring Your Own Device) and mobile devices, IT professionals are challenged to meet two goals:
Many organizations believe they are in control and protected when resources exist within the boundaries of their corporate networks. But in today's digital workplace, that boundary has expanded with managed mobile devices and resources and services in the cloud. Now you need to manage the complexity of protecting your users' identities and data stored on their devices and apps.
Perhaps you're already using Azure AD to manage users in the cloud who need to access Microsoft 365 and other SaaS applications, as well as web apps hosted on-premises. If you already have Azure AD, you can leverage it as one control plane to allow seamless and secure access to your on-premises applications. Or, maybe you're still contemplating a move to the cloud. If so, you can begin your journey to the cloud by implementing Application Proxy and taking the first step towards building a strong identity foundation.
While not comprehensive, the list below illustrates some of the things you can enable by implementing App Proxy in a hybrid coexistence scenario:
This article explains how Azure AD and Application Proxy give remote users a single sign-on (SSO) experience. Users securely connect to on-premises apps without a VPN or dual-homed servers and firewall rules. This article helps you understand how Application Proxy brings the capabilities and security advantages of the cloud to your on-premises web applications. It also describes the architecture and topologies that are possible.
Previously, your control plane for protecting internal resources from attackers while facilitating access by remote users was all in the DMZ, or perimeter network. But the VPN and reverse proxy solutions deployed in the DMZ used by external clients to access corporate resources aren't suited to the cloud world. They typically suffer from the following drawbacks:
In today's cloud-first world, Azure AD is best suited to control who and what gets into your network. Azure AD Application Proxy integrates with modern authentication and cloud-based technologies, like SaaS applications and identity providers. This integration enables users to access apps from anywhere. Not only is App Proxy more suited for today's digital workplace, it's more secure than VPN and reverse proxy solutions and easier to implement. Remote users can access your on-premises applications the same way they access Microsoft and other SaaS apps integrated with Azure AD. You don't need to change or update your applications to work with Application Proxy. Furthermore, App Proxy doesn't require you to open inbound connections through your firewall. With App Proxy, you simply set it and forget it.
In today's digital workplace, users work anywhere with multiple devices and apps. The only constant is user identity. That's why the first step to a secure network today is to use Azure AD's identity management capabilities as your security control plane. A model that uses identity as your control plane is typically comprised of the following components:
With Application Proxy, Azure AD keeps track of users who need to access web apps published on-premises and in the cloud. It provides a central management point for those apps. While not required, it's recommended you also enable Azure AD Conditional Access. By defining conditions for how users authenticate and gain access, you further ensure the right people have access to applications.
Note: It's important to understand that Azure AD Application Proxy is intended as a VPN or reverse proxy replacement for roaming (or remote) users who need access to internal resources. It's not intended for internal users on the corporate network. Internal users who unnecessarily use Application Proxy can introduce unexpected and undesirable performance issues.
Application Proxy is an Azure AD service you configure in the Azure portal. It enables you to publish an external public HTTP/HTTPS URL endpoint in the Azure Cloud, which connects to an internal application server URL in your organization. These on-premises web apps can be integrated with Azure AD to support single sign-on. End users can then access on-premises web apps in the same way they access Microsoft 365 and other SaaS apps.
Components of this feature include the Application Proxy service, which runs in the cloud, the Application Proxy connector, which is a lightweight agent that runs on an on-premises server, and Azure AD, which is the identity provider. All three components work together to provide the user with a single sign-on experience to access on-premises web applications.
After signing in, external users can access on-premises web applications by using a familiar URL or My Apps from their desktop or iOS/MAC devices. For example, App Proxy can provide remote access and single sign-on to Remote Desktop, SharePoint sites, Tableau, Qlik, Outlook on the web, and line-of-business (LOB) applications.
There are several ways to configure an application for single sign-on and the method you select depends on the authentication your application uses. Application Proxy supports the following types of applications:
App Proxy works with apps that use the following native authentication protocol:
App Proxy also supports the following authentication protocols with third-party integration or in specific configuration scenarios:
For more information on supported methods, see Choosing a single sign-on method.
The remote access solution offered by Application Proxy and Azure AD support several security benefits customers may take advantage of, including:
Authenticated access. Application Proxy is best suited to publish applications with pre-authentication to ensure that only authenticated connections hit your network. For applications published with pre-authentication, no traffic is allowed to pass through the App Proxy service to your on-premises environment, without a valid token. Pre-authentication, by its very nature, blocks a significant number of targeted attacks, as only authenticated identities can access the backend application.
Conditional Access. Richer policy controls can be applied before connections to your network are established. With Conditional Access, you can define restrictions on the traffic that you allow to hit your backend application. You create policies that restrict sign-ins based on location, strength of authentication, and user risk profile. As Conditional Access evolves, more controls are being added to provide additional security such as integration with Microsoft Cloud App Security (MCAS). MCAS integration enables you to configure an on-premises application for real-time monitoring by leveraging Conditional Access to monitor and control sessions in real-time based on Conditional Access policies.
Traffic termination. All traffic to the backend application is terminated at the Application Proxy service in the cloud while the session is re-established with the backend server. This connection strategy means that your backend servers are not exposed to direct HTTP traffic. They are better protected against targeted DoS (denial-of-service) attacks because your firewall isn't under attack.
All access is outbound. The Application Proxy connectors only use outbound connections to the Application Proxy service in the cloud over ports 80 and 443. With no inbound connections, there's no need to open firewall ports for incoming connections or components in the DMZ. All connections are outbound and over a secure channel.
Security Analytics and Machine Learning (ML) based intelligence. Because it's part of Azure Active Directory, Application Proxy can leverage Azure AD Identity Protection (requires Premium P2 licensing). Azure AD Identity Protection combines machine-learning security intelligence with data feeds from Microsoft's Digital Crimes Unit and Microsoft Security Response Center to proactively identify compromised accounts. Identity Protection offers real-time protection from high-risk sign-ins. It takes into consideration factors like accesses from infected devices, through anonymizing networks, or from atypical and unlikely locations to increase the risk profile of a session. This risk profile is used for real-time protection. Many of these reports and events are already available through an API for integration with your SIEM systems.
Remote access as a service. You don't have to worry about maintaining and patching on-premises servers to enable remote access. Application Proxy is an internet scale service that Microsoft owns, so you always get the latest security patches and upgrades. Unpatched software still accounts for a large number of attacks. According to the Department of Homeland Security, as many as 85 percent of targeted attacks are preventable. With this service model, you don't have to carry the heavy burden of managing your edge servers anymore and scramble to patch them as needed.
Intune integration. With Intune, corporate traffic is routed separately from personal traffic. Application Proxy ensures that the corporate traffic is authenticated. Application Proxy and the Intune Managed Browser capability can also be used together to enable remote users to securely access internal websites from iOS and Android devices.
Another major benefit of implementing Application Proxy is extending Azure AD to your on-premises environment. In fact, implementing App Proxy is a key step in moving your organization and apps to the cloud. By moving to the cloud and away from on-premises authentication, you reduce your on-premises footprint and use Azure AD's identity management capabilities as your control plane. With minimal or no updates to existing applications, you have access to cloud capabilities such as single sign-on, multi-factor authentication, and central management. Installing the necessary components to App Proxy is a simple process for establishing a remote access framework. And by moving to the cloud, you have access to the latest Azure AD features, updates, and functionality, such as high availability and the disaster recovery.
To learn more about migrating your apps to Azure AD, see the Migrating Your Applications to Azure Active Directory white paper.
The following diagram illustrates in general how Azure AD authentication services and Application Proxy work together to provide single sign-on to on-premises applications to end users.
|Endpoint||The endpoint is a URL or an end-user portal. Users can reach applications while outside of your network by accessing an external URL. Users within your network can access the application through a URL or an end-user portal. When users go to one of these endpoints, they authenticate in Azure AD and then are routed through the connector to the on-premises application.|
|Azure AD||Azure AD performs the authentication using the tenant directory stored in the cloud.|
|Application Proxy service||This Application Proxy service runs in the cloud as part of Azure AD. It passes the sign-on token from the user to the Application Proxy Connector. Application Proxy forwards any accessible headers on the request and sets the headers as per its protocol, to the client IP address. If the incoming request to the proxy already has that header, the client IP address is added to the end of the comma-separated list that is the value of the header.|
|Application Proxy connector||The connector is a lightweight agent that runs on a Windows Server inside your network. The connector manages communication between the Application Proxy service in the cloud and the on-premises application. The connector only uses outbound connections, so you don't have to open any inbound ports or put anything in the DMZ. The connectors are stateless and pull information from the cloud as necessary. For more information about connectors, like how they load-balance and authenticate, see Understand Azure AD Application Proxy connectors.|
|Active Directory (AD)||Active Directory runs on-premises to perform authentication for domain accounts. When single sign-on is configured, the connector communicates with AD to perform any additional authentication required.|
|On-premises application||Finally, the user is able to access an on-premises application.|
Azure AD Application Proxy consists of the cloud-based Application Proxy service and an on-premises connector. The connector listens for requests from the Application Proxy service and handles connections to the internal applications. It's important to note that all communications occur over TLS, and always originate at the connector to the Application Proxy service. That is, communications are outbound only. The connector uses a client certificate to authenticate to the Application Proxy service for all calls. The only exception to the connection security is the initial setup step where the client certificate is established. See the Application Proxy Under the hood for more details.
Application Proxy connectors are lightweight agents deployed on-premises that facilitate the outbound connection to the Application Proxy service in the cloud. The connectors must be installed on a Windows Server that has access to the backend application. Users connect to the App Proxy cloud service that routes their traffic to the apps via the connectors as illustrated below.
Setup and registration between a connector and the App Proxy service is accomplished as follows:
For more information, see Plan an Azure AD Application Proxy deployment.
It's recommended that you always deploy multiple connectors for redundancy and scale. The connectors, in conjunction with the service, take care of all the high availability tasks and can be added or removed dynamically. Each time a new request arrives it's routed to one of the connectors that is available. When a connector is running, it remains active as it connects to the service. If a connector is temporarily unavailable, it doesn't respond to this traffic. Unused connectors are tagged as inactive and removed after 10 days of inactivity.
Connectors also poll the server to find out if there is a newer version of the connector. Although you can do a manual update, connectors will update automatically as long as the Application Proxy Connector Updater service is running. For tenants with multiple connectors, the automatic updates target one connector at a time in each group to prevent downtime in your environment.
Note: You can monitor the Application Proxy version history page to be notified when updates have been released by subscribing to its RSS feed.
Each Application Proxy connector is assigned to a connector group. Connectors in the same connector group act as a single unit for high availability and load balancing. You can create new groups, assign connectors to them in the Azure portal, then assign specific connectors to serve specific applications. It's recommended to have at least two connectors in each connector group for high availability.
Connector groups are useful when you need to support the following scenarios:
For more information about choosing where to install your connectors and optimizing your network, see Network topology considerations when using Azure Active Directory Application Proxy.
Up to this point, we've focused on using Application Proxy to publish on-premises apps externally while enabling single sign-on to all your cloud and on-premises apps. However, there are other use cases for App Proxy that are worth mentioning. They include:
The way we work and the tools we use are changing rapidly. With more employees bringing their own devices to work and the pervasive use of Software-as-a-Service (SaaS) applications, the way organizations manage and secure their data must also evolve. Companies no longer operate solely within their own walls, protected by a moat that surrounds their border. Data travels to more locations than ever before -- across both on-premises and cloud environments. This evolution has helped increase users' productivity and ability to collaborate, but it also makes protecting sensitive data more challenging.
Whether you're currently using Azure AD to manage users in a hybrid coexistence scenario or are interested in starting your journey to the cloud, implementing Azure AD Application Proxy can help reduce the size of your on-premises footprint by providing remote access as a service.
Organizations should begin taking advantage of App Proxy today to take advantage of the following benefits: