If you use the Internet regularly or work in a company and surf the Internet while you're at work, you must have surely come across the term firewall. You may have heard people say "firewalls to protect computers from hackers and attacks web" or "a website is blocked by firewalls in the workplace." If you've ever wondered what exactly is this firewall and how it works, let's go. In this post I will try to explain "how firewalls work" in simple language.
How Firewalls Work
The firewalls are basically a barrier between your computer (or network) and the internet (outside world). A firewall can be simply compared to a guard at the entrance of your home and filter the visitors coming to your place. You can allow visitors to enter some other, while denying that he had suspected intruders. Similarly, a firewall is software or a device that filters the information (packets) from the Internet to your computer or computer network.
The firewall may decide to allow or block network traffic between the devices, under rules that are pre-configured by the administrator or the firewall. Most personal firewalls like Windows Firewall running on a set of predefined rules that are most appropriate under normal circumstances, so the user does not need to worry much about the configuration of the firewall.
Personal firewalls are easy to install and use, and therefore preferred by end users for use on personal computers. However, the networks of large companies and prefer firewalls that have many options to configure it to meet individual needs. For example, a company can define rules for different firewall servers for FTP, Telnet servers and servers Web. In addition, the company can even control how employees connect to the Internet by blocking access to certain Web sites or restrict the transfer of files to other networks. Thus, apart from security, a firewall can provide the company to control how people use the network.
Firewalls use one or more of the following methods to control incoming and outgoing traffic on a network:
1. Packet filtering: In this method the packets (small bits of data) are analyzed against a set of filters. Packet filters are a set of rules that come with and refuse to accept the actions that are pre-configured or can be manually configured by the administrator of the firewall. If the packet arrives to do through these filters, it is possible to reach the destination, otherwise discarded.
2. Stateful Inspection: This is a new method does not analyze the contents of packets. Instead, it compares key aspects of each packet to a database from a reliable source. Both incoming and outgoing packets compared to this database and if the comparison yields a reasonable match, the packets may travel further. Otherwise it will be rejected.
Firewall Configuration
These firewalls can be configured by adding one or more filters based on various conditions, as indicated below:
1. IP addresses: In any case, if an IP address outside the network is said to be negative, then it is likely to filter to block all traffic to and from this address IP. For example, if a cetain IP address must be too many connections to a server, the administrator can decide to block traffic from that IP address using the firewall.
2. Domain names: Since it is difficult to remember the addresses IP, is an easier and more intuitive to configure the firewall to add filters based on domain names. By creating a filter area, a company may decide to block all access to certain domain names, or provides access to a list of names chosen field.
3. Ports / Protocols: Any service that runs on a server is available on the Internet using numbered ports, one for each service. In simple words, the ports can be compared with the virtual doors of the server through which services are available. For example, if a server running a Web (HTTP) service, you will normally be available on port 80. To use this service, the client must connect to the server via port 80. Similarly, services such as Telnet (port 23), FTP (port 21) and SMTP (port 25), services can be run on the server. If services for the general public, is usually kept open. Otherwise, we excluded the firewall to prevent intruders to use open ports to establish unauthorized connections.
4. Specific words or phrases: A firewall can be configured to monitor one or more specific words or phrases, so that both incoming and outgoing packets scanning for words in the filter.For example, you can configure a firewall rule to filter all packets that contain offensive word or phrase that you can decide to block the entry or exit your network.
Hardware vs. software firewall
Hardware firewalls provide the highest level of security and therefore preferred for servers where security is a top priority, while software firewalls are cheaper and are now preferred to personal computers and laptops. Hardware firewalls usually come as a unit to build a router and a maximum security because it filters each packet in the material itself before it goes to your computer. A good example is the Linksys Cable / DSL Router.
Why Firewall?
Firewalls provide security in a range of online threats, such as remote login, the backdoor Trojan, intrusion, DOS and DDOS attacks, viruses, theft, cookies and more. The effectiveness of the security depends on how to configure the firewall and how to set filtering rules. However, the main threats, such as DOS and DDOS attacks are sometimes manage to bypass the firewall and do damage to the server. Even if the firewall is not a complete answer to online threats, can more effectively manage the attacks and computer security as possible.
