A proxy firewall is a security system that manages, filters, and caches requests made to the internet from internal networks. It monitors data traffic using its IP address and operates at the application level. This article will discuss a proxy firewall, why it’s used, how it differs from traditional firewalls, how it functions, and any new developments in this field. It will also discuss how proxy firewalls relate to proxy servers.
Definition and purpose of a proxy firewall
A proxy firewall is a device between a client and a server on the internet. It is also referred to as an application firewall or a gateway firewall. Using pre-established security policies as a guide, it intercepts, examines, and decides whether to allow or deny requests and responses from various protocols, including HTTP, FTP, and SMTP. A proxy firewall also stores web pages and documents in cache to enhance network efficiency and minimize bandwidth usage.
A proxy firewall’s primary goal is to defend network resources against malevolent attacks and unauthorized access. It conceals the location and identity of the internal network from the external network by using its IP address rather than the client’s. By looking through the application-layer data, it can identify and stop threats that traditional firewalls cannot, such as malware, viruses, worms, spyware, phishing, and denial-of-service (DoS) attacks.
Relation between a proxy firewall and a proxy server
A proxy server is a hardware or software system that serves as a middleman between a client and a server on the internet. It can carry out many tasks, including content modification, encryption, caching, filtering, logging, authentication, and load balancing. Moreover, a proxy server can get around network limitations and enhance efficiency.
One form of proxy server that prioritizes security is a proxy firewall. Not all proxy servers are proxy firewalls, even though all proxy firewalls are proxy servers. Compared to a standard proxy server, a proxy firewall inspects and protects network traffic at a deeper level. Additionally, a proxy firewall supports fewer protocols than a proxy server with a broader purpose.
How a Proxy Firewall Works
A proxy firewall operates by acting as a single point of contact between the internal network and the internet. The internal network and the external network are served by its two network interfaces. A request is sent to the proxy firewall by an internal network client to access an internet website or application. Next, the proxy firewall determines whether the request is permitted by reviewing its security policy. The proxy firewall establishes a new connection on the client’s behalf to the destination server and forwards the request if the request is approved. After that, the proxy firewall receives a response from the destination server and scans it for any malicious activity or content indications. The proxy firewall sends the answer to the client if it is legitimate and clean.
TCP handshaking is the process of establishing a new connection between the destination server and the proxy firewall. Three steps are involved: acknowledge (ACK), synchronize (SYN), and synchronize-acknowledge (SYN-ACK).
With its IP address and port number, the client transmits a SYN packet to the destination server. In response, the destination server sends a SYN-ACK packet containing its port number and IP address. Subsequently, the client confirms the connection by sending an ACK packet.
This process is altered when utilizing a proxy firewall, though. The client’s IP address and port number are sent in a SYN packet to the proxy firewall. The destination server’s IP address and port number are included in a SYN-ACK packet sent back by the proxy firewall. The connection with the proxy firewall is confirmed by the client sending an ACK packet but not with the destination server.
Next, using its IP address and port number, the proxy firewall sends a second SYN packet with its IP address to the destination server. The destination server returns another SYN-ACK packet with its IP address and port number. The proxy firewall then sends one more ACK packet to verify that it is still connected to the destination server.
This way, the client thinks it is connected to the destination server directly but is connected through the proxy firewall. The destination server thinks it is connected to the proxy firewall directly but is connected through the client.
Types of Proxy Firewalls
Proxy firewalls come in various formats according to the protocols and applications they can handle. Among them are:
- Application Layer Proxy: According to the OSI model, this proxy firewall examines and filters traffic at the application layer (layer 7). It is compatible with many applications and protocols, including Telnet, POP3, IMAP4, HTTP, FTP, and SMTP. It can carry out virus scanning, content filtering, caching, encryption, compression, and authentication.
- Circuit-Level Proxy: According to the OSI model, this proxy firewall examines and filters traffic at the transport layer (layer 4). Generic TCP and UDP connections are supported. It merely confirms that the TCP handshaking is legitimate; it doesn’t look at the contents of the packets. It can carry out tasks like masking, tunneling, and encryption.
- Stateful Inspection Proxy: This proxy firewall integrates circuit-level and application-layer proxy functionality. It examines and filters network traffic at the OSI model’s application and transport layers. Both general TCP and UDP connections and particular applications and protocols are supported. It can perform tasks like content filtering, virus scanning, tunneling, masking, encryption, compression, caching, and authentication.
Proxy Firewalls vs. Traditional Firewalls
A traditional firewall is an apparatus that filters traffic at the network layer (layer 3) or data link layer (layer 2) of the OSI model. It uses protocols, port numbers, and IP addresses to enforce security policies. Neither the application-layer data nor the packet content is examined. It can carry out port forwarding, network address translation (NAT), and packet filtering.
Because a proxy firewall can inspect and filter traffic at higher OSI model layers, it is more secure than a traditional firewall. Additionally, it can conceal the location and identity of the internal network from the outside network. A proxy firewall must establish a new connection for every request and response, which makes it slower than a conventional firewall. Specific applications’ and protocols’ compatibility and functionality may also be impacted.
Emerging Trends in Proxy Firewalls
Proxy firewalls must change and adapt to new demands and challenges as cyber threats become more complex and varied. The following are a few new developments in proxy firewalls:
- Cloud-based Proxy Firewalls are proxy firewalls hosted and maintained on the cloud by an outside service provider. They provide ease of deployment and maintenance, flexibility, cost-effectiveness, and scalability. Additionally, they can offer access to several geographically dispersed data centers and servers for improved availability and performance.
- Web Application Firewalls (WAFs): A type of proxy firewall, web application firewalls are intended to defend web applications against frequent online threats like cross-site scripting (XSS), cross-site request forgery (CSRF), and SQL injection. Additionally, they can offer functions like web application patching, web application acceleration, and scanning.
- Next-Generation Firewalls (NGFWs): These firewalls integrate the capabilities of intrusion prevention systems (IPS), antivirus programs, sandboxing programs, and traditional firewalls. They can thoroughly defend against various cyberattacks at different OSI model layers. Additionally, they can offer features like threat intelligence, identity awareness, application awareness, and user awareness.
Conclusion
A proxy firewall is a security system that manages, filters, and caches requests made to the internet from internal networks. It monitors data traffic using its IP address and operates at the application level. It can defend against malicious attacks and unauthorized access to network resources by examining and preventing application-layer data. By caching documents and web pages, it can also enhance network performance.
Based on how they manage various protocols and applications, proxy firewalls come in multiple forms, including stateful inspection, application layer, and circuit-level models. Although slower and more complicated than a traditional firewall, a proxy firewall offers greater security.
Proxy firewalls must change and adapt to meet the demands of the ever-evolving cyberspace. Cloud-based proxy firewalls, web application firewalls, and next-generation firewalls are a few of the new developments in proxy security.
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