A Firewall (from English firewall "„the fire wall "“) is a system from software and hardware components, which limit the access between different computer networks to convert around a security concept.

Hardware components of a Firewall are computers with network interfaces as rout or host; Software components are for example package filters or Proxyserver. A frequent targeted application of a Firewall consists of it controlling the data traffic between one for local network (LAN), which can be protected, and the Internet.

Basic idea

Firewalls sit at the interfaces between individual nets or computer systems and control the data traffic between the subranges, in order to prevent undesired traffic and to let only desired traffic happen. The most frequent employment of a Firewall consists of it controlling traffic between a local area network (LAN) and the Internet. A complex scenario represents the Demilitarized zone (DMZ). In principle the transition LAN Internet does not only justify the employment of a Firewall. Also between two or several organization-internal nets a Firewall can be used, in order to carry for the different protection need of the zones calculation.

Accordingly a Firewall possesses two substantial tasks:

• Prevent the range protected by inadvertent data traffic from external computer systems to
• Prevent the range protected by inadvertent data traffic from to external systems

Approximately around the topic Firewall exist many terms, which are partly correct, but very often only the half truth obtain. Colloquially frequently the software is meant with a Firewall, which controls and regulates the data traffic between the separate ranges. One must differentiate thus between (safety) the concept Firewall and the concrete realization of the Firewall. The security concept describes rules, which information may not pass the Firewall and which. The concept is realized by a software, which runs on (often special) a hardware. The hardware is responsible thereby for receiving and sending the individual packets (and thus actually no securing element) and the software regulates traffic. (Which let Which is not let hardware is frequent as optimized with other network elements (routing or gateway) also for setting of tasks (examination from packages, the hochperformantes receiving and sending packages, etc. snaps).

In principle one separates the Firewalltypen specifically, i.e. a Softwarefirewall secures individual PC"´s and workstations, since it is installed as software on the systems. A Hardwarefirewall protects hardware, thus the network as such. This does not have obligatorily which with the technology to do, it serves only the

Host Firewall (software) and network Firewall (hardware)

Colloquially frequently of hardware or software Firewall one speaks. With this distinction it concerns primarily a non-technical definition. The distinction of hard and software Firewall is technically seen unreasonable. To each Firewall software belongs, and this must be implemented on hardware. Falsely become dedicated rout, on which the Firewallsoftware is implemented, when hardware Firewall designates. Personal Firewalls are often called software Firewall, but implemented on the PC. They need thus the PC as hardware.

More importantly than the designation than hard or software Firewall is the which is the basis operating system. Software Firewalls are installed as described above on PC's and are affected thereby naturally also by the safety gaps of the operating system. Hardware Firewalls can be based also on standard operating systems (there usually Unix) and thus also from problems of these operating systems concerned. In addition still nose and safety gaps come in the actual Firewall software.

There are however also hardware Firewalls, which function with particularly an operating system developed for it, i.e., the operating system is at the same time also the Firewall Software.Auch this can naturally nose and safety gaps contain, however the additional source of error (operating system/Firewall software) is omitted by the uniform structure (Firewall operating system).

Hardware Firewalls are therefore regarded as safer than software Firewalls.

Network Firewall

Usually equipment is called "„hardware Firewall "“, if it concerns a specific product for exactly this purpose. It is equipment with several network interfaces and a software running on it which serve mainly as Firewall.

The hardware component has as a rule three network interfaces, at which the nets which can be separated are attached in each case. The three interfaces for safety reasons (often however because of the lattice structure and thus from the conceptional necessity) selected, with the fact ensured is that only such packages are let through by a net in the other one, which is recognized of the software as valid.

One differentiates between three network zones:

1. the external net (WAN), nowadays frequently Internet, which is not considered as trustworthily (Untrusted)
2. the so-called demilitarisierte zone (DMZ), in which from the external net attainable servers are accommodated
3. the internal net (LAN), which is considered as trustworthy (Trusted)

There can be also several DMZs (typically 3-6) with different in each case rights to give over e.g. well waited Serven of more rights in the LAN than servers, which are waited rather irregularly. Likewise often different service types, if they are accommodated on different hardware, are platziert likewise in different DMZs. The use of several DMZs limits the possibilities of the aggressor with compromising an individual DMZ. In extreme cases this goes up to a complete bulkheading of a DMZ from the LAN (= connection only to the WAN).

Often it concerns with a hardware Firewall however a software Firewall, which is gebundelt with special hardware.

Articles in category "Firewall"

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