What is ZoneAlarm ?

One of the best free firewall products available is ZoneAlarm from Zone Labs which is available free of cost and can be downloaded from the company's site at 

www.zonelabs.com.

It provides protection for Internet users. Combining the safety of a dynamic firewall with total control over applications Internet use. ZoneAlarm gives rock-solid protection against thieves and vandals. ZoneAlarm makes ironclad you from malicious programs, like Spyware and Trojan horses, by allowing you to control your computers Internet traffic and how application access the Internet  

What is Stageful Inspection firewall ?

These are the new generation of firewall technology patented by Check Point Software Technologies. Stageful Inspection provides full application layer awareness without requiring a separate proxy for every service to be secured. This results in multiple benefits to customers encluding excellent performance, reliability and the ability to support new and custom applications and services quickly and easily. Stageful inspection architecture is unique in that it understands the state of any communication through the firewall machine, including packet, connection and application information. Packet filters do not track application or connection state. Application proxies rack only application state, not packet or connection state which may introduce some vulnerabilities.

What is Proxy Firewall ?

This type of firewall acts as a intermediary of user requests, setting up a second connection to the desired resource either at the application layer (an application proxy) or at the session or transport layer (a circuit relay). Proxy firewalls tend to take a performance hit since it relies on application layer. They are restrictive when it comes to allowing or denying evolving or new types of application.

What is Application Level Firewall (Application Gateway) ?

 Application level firewall (Application Gateway) is a part of a proxy server. Application gateways do not allow any packets to pass directly between the two networks they connect. Instead, proxy appliactions running on the firewall computer forward requests to services on the private network. Then forward responses to the originators on the unsecured public network. Application gateways authenticate the credentials of a user before allowing access to the network. They are auditing and logging mechanisms as part of the security policy. Application gateways require some configuration on the part of users to able their client machines to function properly. For example, if a File Transfer Protocol (FTP) proxy is configured on an application gateway, it can be configured to allow some FTP commands but deny others. One could configure a SMTP (Simple Mail Transfer Protocol ) proxy on an application gateway that would accept mail from the outside (without revealing internal e-mail addresses), and then forward the mail to the internal mail server. However, because of the additional processing overhead, application gateways have advanced hardware requirements and are slower than network-level firewalls.  

Types of Firewall

Firewall uses a variety of architectures to manage access control. Thses are :

a. Packet-Filtering Firewalls
b. Proxy firewall
c. Stageful Inspection

Packet-filtering Firewall

This type of firewall examines all the packets it comes across. It forwards them or drops them based on pre-defined rules. This redimentary firewall provides only basic protection. Packet-filtering firewalls are restrictive since network managers can only define a few parameters.
Many routers and proxy servers use some form of packet filtering that provides firewall capabilities for protecting the network from unauthorized traffic. Administrators can create rules for filtering out unwanted packets and can arrange these rules in the most efficient order. A packet that passes all the rules is only allowed through, while a packet that violates any rules is dropped. 
Packet filtering can be implemented on routers and other devices in two ways:

1. Static filtering
2. Dynamic filtering

Static filtering

Static paket filtering provides limited security by configuring selected ports as either permanently open or permanently closed. For example, to deny outside packets access to a company internet server on port 80 (the standart port number for the Hypetext Transfer Protocol or HTTP) one could configure the router of firewall to block all incoming packets directed port 80.

Dynamic filtering

Dynamic packet filtering provides enhanced security. It acts by allowing selected ports to be opened at the start of a legitimate session and then closes them at the end of the session. This is particularly useful for protocols that allocate ports dynamically - for example, with the File Transfer Protocol (FTP). 

What Constitutes a Good Firewall System ?

Firewall can protect network environment. But what constitutes a good firewall? The answer actually depend on the site security requirements. However, one should always check for the following attributes in a firewall:

1. The firewall should be able to support a 'deny all services except those specifically permitted' design policy, even if that is not the policy used.

2. The firewall should be flexible. It should be able to accommodate new services and needs if the security policy of the origination warrants so.

3. The firewall should contain advanced authentication measures.

4. The firewall should employ filtering techniques to permit or to deny services to specified host systems as and when needed.

5. The firewall should use proxy services for File Transfer Protocol (FTP) and TELNET (TELecommunication NETwork), so that advanced authentication measures can be employed and centralized. If services such as gopher or HTTP are required, the firewall should contain the corresponding proxy services.

6. The firewall should accommodate public access to the site, such that public information servers can be protected by the firewall but can be segregated from site systems that do not require the public access.

7. The firewall should contain mechanisms for logging traffic and susoicious activity, and should contain machanisms for log reduction so that logs are readable and understandable.

8. If the firewall requires an operating system such as Unix, a secured version of the operating system should be part of the firewall.

What is Firewall ?

Firewall are hardware and software combinations that are built using routers, servers and variety of software. They sit at the most vulnerable point between a corporate network and the Internet and they can be as simple or complex as system administrators want to built them. Firewalls reduce the speed of access of networks.

Router or remote-access server (or several routers or access servers) designated as a buffer between connected networks. A firewall uses access lists and other methods to ensure the security that enforces a boundary between two or more networks.

A firewall can either be software-based or hardware-based and is used to help keep a network secure. Its primary objective is to control the incoming and outgoing network traffic by analyzing the data packets and determining whether it should be allowed through or not, based on a predetermined rule set. A network's firewall builds a bridge between an internal network that is assumed to be secure and trusted, and another network, usually an external (inter)network, such as the Internet, that is not assumed to be secure and trusted.

Many personal computer operating systems include software-based firewalls to protect against threats from the public Internet. Many routers that pass data between networks contain firewall components and, conversely, many firewalls can perform basic routing functions

Every time a corporation connects its internal computer network or LAN to the Internet, it faces potential danger regarding security. Due to the Internet's openness, every corporate network connected to it is vulnerable to attack. Crackers on the Internet could break into the corporate network and do harm in a number of ways. Some such methods are the  following:

a. They could copy or damage important data.
b. Damage individual computer data or the entire networking.
c. Use the corporate computer's resources or use the corporate network and resources as a way of posing to be a corporate employee.

The solution for all these problems and many more is to built 'firewalls' to protect its network. These firewalls allow anyone on the corporate network to access the Internet, but they stop crackers, hackers or others bent on to do mischief on the Internet from gaining access to the corporate network and causing damage.

Benefits of using a Firewall

i. Protection from services which are inherently more prone to attacks.
ii. Access to host in the network can be strictly controlled.
iii. Security is concentrated on a single firewall system. This leads to better implementation of authentication procedures.
iv. Logging and statistics of network use and misuse.
v. Policy enforcement.