<p>Firewalls protect network traffic and decide witch traffic to send further and witch traffic will be blocked. All this depends on the rules in the firewall. The firewall is installed between the internal network and the Internet. It is difficult to find a firewall that can protect us against different threats. Firewalls have both advantages and disadvantages and all this make them vulnerable. It is important to understand how the firewall protects the network and how to configure it. This paper gives the reader a clear idea how firewalls can protect against different attacks and improve the security.</p><p>Computers are not safe when connected to Internet. This paper is about how to use a personal firewall to protect a computer when connected to Internet. One of the firewalls in this examination is Norton Personal Firewall 2005.</p><p>Perkins, “Firewalls 24seven, 2nd Edition” and Brian Komar, Ronald Beekelaar and Joern Wettern “Firewalls for Dummies”. Information has also been collected from Apples home page.</p><p>It is important to have knowledge about different attacks against network traffic and also about how to protect against them. To know the risks is the first step to be able to evolve an own strategy; too defend network attack.</p>

Attacker och intrång på webbservrar är idag vanligt förekommande. Webben gör det lätt för hackare, knäckare och andra inkräktare att hitta sårbara servrar, och det finns gott om tips att hämta för den som vill lära sig hur man gör intrång. Det finns ett flertal olika intrångsmetoder som utnyttjar olika typer av svagheter i datorsystemen. Denna uppsats inriktar sig på svagheter i webbplatsernas serverskriptsystem, dess skriptkod och konfiguration. Syftet är att undersöka huruvida intrång kan göras med endast en webbläsare via webbplatsens offentliga webbsidor. Genom att kombinera tre olika metoder - litteraturundersökning, en enkät och ett experiment - undersöker uppsatsen hur serverskriptintrång fungerar. Den analyserar ett urval vanliga misstag webbprogrammerare kan göra, till exempel att inte kontrollera inkommande data, eller att använda lättgissade variabelnamn och databastabellnamn. Några olika typer av intrång analyseras, som till exempel SQL-injektion. Förebyggande åtgärder tas även upp med ett antal konkreta exempel. Uppsatsens slutsats är att på webbplatser med svaga serverskriptsystem kan inkräktare göra intrång via webbplatsens egna publika webbsidor, med endast en vanlig webbläsare som hjälpmedel. I uppsatsens avslutande del diskuteras även några orsaker till varför det produceras ogenomtänkt skriptkod, till exempel beroende på att programmeringskurser i allmänhet inte tycks lära ut säker programmering i tillräcklig utsträckning.

Firewalls protect network traffic and decide witch traffic to send further and witch traffic will be blocked. All this depends on the rules in the firewall. The firewall is installed between the internal network and the Internet. It is difficult to find a firewall that can protect us against different threats. Firewalls have both advantages and disadvantages and all this make them vulnerable. It is important to understand how the firewall protects the network and how to configure it. This paper gives the reader a clear idea how firewalls can protect against different attacks and improve the security. Computers are not safe when connected to Internet. This paper is about how to use a personal firewall to protect a computer when connected to Internet. One of the firewalls in this examination is Norton Personal Firewall 2005. Perkins, “Firewalls 24seven, 2nd Edition” and Brian Komar, Ronald Beekelaar and Joern Wettern “Firewalls for Dummies”. Information has also been collected from Apples home page. It is important to have knowledge about different attacks against network traffic and also about how to protect against them. To know the risks is the first step to be able to evolve an own strategy; too defend network attack.

As more and more people gain access to broadband in their properties, the security threats get bigger. A lot more people also have computers that they carry home from work where they store important information concerning the company. The information stored on theese computers can be very easy to retrieve if you have the will and the skill to do it. Very few people have any knowledge how to protect themselves from theese threats.