The modern use of computers and communication networks has seen an increasing demand for having almost all computers, both in domestic use and in office use, connected to a network at all times, especially to Internet. The advantages of being “always” connected are many, for example fast access to the information available on Internet, the ability to receive and send e-mails without noticeable delays and notification of other incoming messages such as fax transmissions, Internet calls etc. However, the massive flow of information in combination with most computers having network connections has increased the vulnerability of the communication networks and the individual computers. Examples of the vulnerability of the systems include the devastating effects of computer viruses of various kinds, intrusion by “hackers” into corporations and governments computer systems, fraudulent use of credit cards/bank accounts by monitoring money transfer via Internet and unauthorized access to crucial business information. Another type of misuse of the computer networks that recently has arisen is, without knowledge of the owner, to use a company's server or someone's domestic computer for storing and distributing files. This is typically done by intruders for the purpose of not having to provide the storage capacity themselves and/or to store and distribute material of dubious or illegal character, such as unauthorized copies of music or movies. A specially dangerous and deceptive type of virus is the so called Trojan horses and worms. This types of virus typically enters the computer in an e-mail or a file fetched from the Internet. In the computer the virus program can for example send files and/or information such as passwords to an Internet address. An intruder may then use the information send by the Trojan horse to access the computer and since the virus has provided the intruder with all relevant information this intrusion will appear like an authorized access to the computer.
Today attempts to intrude a computer or server often include the use of a number of viruses as well as other methods of gaining access to, and even control over, the target. Such a destructive program package may include one virus shutting down antivirus and virus warning software, one program looking for ways of getting access to the computer and yet another program searching for passwords, usernames and addresses.
Many computers today are provided with cameras, microphones or other communication devices, typically for the purpose of being able to communicate with voice and picture over the Internet. If an intruder gets control over such equipped computer, for example by use of a Trojan virus, it will be fairly easy for the intruder to use for example the computers microphone for overhearing and recording a conversation taking place in the room where the computer is situated. This can obviously be used for espionage and other forms of criminal activities.
The predominant way of addressing security issues in today's communication networks is by the use of “firewalls”. Firewalls often combine use of proxy servers and filtering techniques such as stateful inspection filter to reduce the possibilities for unwanted access and attacks of viruses. For a comprehensive description of common current security measures see for example “Datakonmmunikation i praktiken”, chapter 20, Kent Mayer, Pagina.se 2001. Although, in many ways effective, the Firewalls need to be continuously updated and maintained by skilled personnel in order to maintain an acceptable level of protection. This is time-consuming and costly, both in man-hours and in upgrading equipment. For smaller businesses, and for persons wanting to have their home computers connected to a network, the installation of firewalls, and in particular the maintenance of them, can be too costly or too complicated, to be considered economically justifiable.
Another area of security is within internal networks, often so called intranets. An organisation's intranet may be protect from outside attacks by firewalls. However, information, which is not meant to be seen by everyone, is often created and shared within the organisation. It is often fairly easy to, within an intranet, look into or copy the work of others.
Thus, although the introduction and widespread use of Firewalls, and the associated proxy servers and techniques for filtering, has greatly increased the level of security in communication networks, there is a need for solutions further improving the security. Not at least for small entities and home users, not having the economical means or technical competence needed for installing and maintaining a security system based on Firewalls.