What is an Application Level Gateway (ALG)?
When you hear “Application Level Gateway,” or ALG for short, think of it as a network traffic conductor. It’s the unsung hero that examines data packets, making sure they follow specific rules and get to where they’re supposed to go – securely and efficiently.
What is an Application Level Gateway (ALG)?
Application-level gateway, also known as proxy firewall, is a type of network security solution that takes action on behalf of the apps and programs they’re set to monitor in a network. They’re primarily responsible for filtering messages and exchanging data flow at the application layer.
By being permitted to access the traffic, activity, and behavior of a network’s applications, proxy firewalls can maintain the integrity, security, and privacy of the network’s servers, apps, and databases from malicious traffic, malware, and unauthorized access attempts.
How does an ALG work?
As the name suggests, application level gateways work by being the only gateway between the network’s internal activities, like users and applications, and the public internet. All traffic that’s incoming or outgoing to the application layer in the network passes through the gateway and gets scanned for any malicious or unauthorized activity.
It’s also called a proxy firewall because it utilizes proxies to set up a private connection that remote users can access the network through, without compromising on speed or security. However, this type of firewall only works on Layer 7 of the Open Systems Intercommunication (OSI) model, which is the layer where the network’s applications, software, and programs operate and access the internet.
This process allows the firewall to avoid direct connections between your network’s applications and outside traffic before it’s completely verified. As a result, this creates an added barrier that makes it harder for intruders and infiltrators to either access your network or even extract information from any exchanged data packets.
With this setup, only one server per network segment has direct access to the public internet. All other devices would have to route their traffic through it, whether it’s outgoing or incoming.
Application Level Gateway Features
- Protocol Inspection: ALGs specialize in understanding and inspecting specific application-layer protocols. By analyzing the data within these protocols, they can validate and assess the legitimacy of the traffic. This enables ALGs to differentiate between authorized and unauthorized data packets and take appropriate actions based on the configured security policies.
- Security Policies Enforcement: Organizations define security policies to meet their unique requirements. ALGs ensure the enforcement of these policies by allowing or blocking specific types of traffic. By monitoring for unauthorized access attempts and scanning for malware or malicious content within the application layer traffic, ALGs help maintain a secure network environment.
- Address Translation: ALGs provide an additional layer of security through network address translation (NAT). By obscuring the internal network structure from external entities, ALGs mitigate the risks associated with exposing real IP addresses to potential attackers.
- Session Control: ALGs play a vital role in managing application-level sessions. They monitor and control data exchanges between applications to ensure that they adhere to predefined rules and policies. ALGs also maintain logs of application-level activities for auditing and compliance purposes, providing a valuable resource for investigating security incidents and ensuring regulatory compliance.
Why are Application Layer Gateways important?
Applications are vital to business operations and daily life, but attacks increasingly target those applications and the application layer of IT infrastructures. To ensure business continuity and protect sensitive data and personally identifiable information (PII), security measures must specifically address the application layer. Application layer gateways are one option for defending applications and the data they contain to ensure secure application delivery.
Benefits of using an Application Level Gateway
ALG can benefit organizations looking to secure their networks and improve network performance. This solution can bring much value if you’re looking to protect your organization from cyber threats or optimize traffic load.
- Increases security – ALGs provide an unparalleled degree of security by examining the content of the packets that pass through them rather than just headers. This allows a much deeper level of inspection, detecting specific applications and protocols and applying various security policies and controls based on the application’s needs.
- Allows traffic logging – Logging the connection of a specific server is much easier than logging the logs of all the enterprise’s endpoints separately. An intermediary server stores all logs of every transaction on the server, allowing IT teams to review granular details of all access attempts. This can help to detect employee usage habits and identify potential threats.
- Supports content caching – In today’s digital environment, optimal application performance is paramount, which is where content caching comes into play. This allows the ALG to cache frequently accessed content, so it can be retrieved locally instead of fetching from the original server when requested.
- Network performance improvements – ALG can distribute incoming traffic across multiple backend servers to ensure that no single one is overloaded. For users, this means better uptime, ensuring that the service is always up and running when needed. In addition, ALG can offload SSL processing from the backend servers, freeing up resources and implementing performance.
- Layered access model – With ALG, web applications are protected with additional barriers that push the threats further away from the organization’s network. This provides multiple layers of protection, making it much more difficult for attackers to bypass security measures to access sensitive data or systems. Organizations can exploit this by preventing attacks from impacting their web applications.
Disadvantages of Application Level Gateways
Application level gateways still have a handful of drawbacks and weak points, especially when used as a stand-alone security solution with no added tools or features.
For one, they’re more prone to experiencing bottlenecks as all the network’s incoming and outgoing data is redirected towards a single point of processing. The stricter the monitoring rules on the proxy server, the slower the data flow.
ALGs also have major compatibility problems, as they can’t support a wide variety of connection types and network protocols. This can greatly limit the pool of servers and agents your application layer can connect with, without needing additional tools.
Similarly, not all applications are compatible with proxy servers. By not being proxy-aware, applications can sometimes ignore the presence of the proxy server and attempt to connect to the internet directly.
While some application level gateways’ drawbacks can be fixed or reduced in effect through proper configuration, that’s not easy to do. Furthermore, any misconfigurations in the setup of the firewall may leave some gaps in your security, such as open ports.
Conclusion
While Application Level Gateways apply packet inspection and offer granular control over application protocols, they are simply one aspect of overall network defense. ALGs alone cannot handle all security issues and must be combined with other network security solutions to provide comprehensive protection. To build a strong network defense plan, integrate ALGs with other firewalls, intrusion detection systems, and other security measures.