Firewalls control incoming and outgoing network traffic to prevent malicious threats like hackers and viruses. They establish a barrier between your trusted and untrusted networks—usually the Internet.
Data moves around a computer network in packets, which include control information (a packet header) and the actual data. The firewall compares the box to a set of rules and filters out unwanted information.
A firewall sits between your business network and the outside world; all data packets have to go through it before they can enter or leave. It implements an access control policy and works at the network layer of the OSI model, analyzing each incoming data packet, looking for security threats, and then deciding whether to allow or deny it. That’s why it’s essential to know and understand how does a firewall work.
A packet filtering firewall identifies malicious information by examining each incoming data packet’s header, which contains essential details like the source and destination IP address, protocol, port number, and MAC address of the physical interface the packet is traversing. The firewall then compares these data points to a set of rules, and if the packet matches, the action is taken. For example, an incoming data packet attempting to establish a Telnet connection with your server will be rejected based on the rule set.
A proxy firewall goes one step further by examining the actual content of each incoming data packet rather than surface-level data points. This way, it can better ensure incoming data packets don’t contain malware. It also allows for more precise control over traffic, but it has some drawbacks: proxy firewalls can slow down your network and require a lot of system resources to run.
Both individuals and organizations use proxy servers to boost internet connection stability, enhance security and privacy and optimize performance. For example, some proxy servers change the user’s IP addresses and other identifying information to make it more difficult for web servers to track their browsing habits. This allows individuals to browse more privately and work around government censorship (especially now that Net Neutrality has been removed).
The proxy server sends the request on behalf of the user to the web server, then receives and gathers the website data and forwards it back to the client. This also helps speed up access as the server already has the web page stored on its local server.
Another benefit of proxy servers is that they act as content filters to block unauthorized internet traffic. This is especially useful for companies that want to protect their networks from hacking, identity or brand theft, and other malware attacks.
While proxies have benefits, they can be prone to security issues as they intercept the original data packets. This can be a problem for unsecured networks and some free proxies that use ad revenue models to make money, which means they often include ads loaded with malware that can infiltrate devices. Luckily, a VPN combines the functionality of a proxy with additional encryption to create a more secure and robust solution.
Stateful inspection is a method of firewall filtering that examines packets at the higher transport and network layers of the OSI model. While basic stateful inspection only looks at protocol headers, it can also read data payloads to a limited extent.
When a packet arrives at the firewall, it does a 5-tuple lookup of its source IP address, destination IP address, source port number, and destination port number and protocol in a flow or connection table. If it finds an entry, it promotes that connection’s internal state to be established. The firewall then performs a series of checks that vary according to the firewall implementation.
For example, simple fast path processing may involve rate checks, layer 3 IP sanitation checks to avoid fragmentation and reassembly-based attacks, and layer seven protocols like IPSec or SSL to protect against spoofing and DOS attacks. Once a new connection is established, it can pass through the firewall and apply its configured security policy.
Some advanced stateful inspection firewalls, implemented as specialized hardware and software, can also do deep packet inspection (DPI) that goes beyond the packet’s header and analyzes its contents, looking for malware signatures to block threats such as Trojans and backdoors. This can be performed on the same appliance that does a stateful inspection, or it can be done on a separate device.
A firewall is a barrier or gatekeeper that works like a traffic controller for the data that tries to gain access to your operating system. It evaluates this incoming data, filters it, and keeps out anything that poses a threat or could be malicious software, such as hackers or viruses.
Firewalls can be software or hardware and come in two forms- a physical device that connects your network and gateway or a program installed on each computer. These devices intuitively parse the good and bad data to allow the former and block the latter based on administrators’ rules. Firewalls are a critical part of a business’s overall network security. They act as safety barriers between private networks and the public internet, where hackers constantly try to penetrate to cause harm.
Packet filtering firewalls, the most common type, examine each packet of data and prohibit them from entering your operating system if they don’t match a set of established security rules. They look at each packet’s source, destination IP address, and other information to determine if it’s allowed or blocked. They also consider the connection states of data streams to determine if they are valid and can be trusted. This is similar to a bouncer looking at a group of high school students and seeing who have already established dance club members before letting in new ones.