Recently among the users of local networks and particular citizens grows uneasiness apropos of the appropriate security assurance of information, which is stored in the computers. The preoccupation is completely justified, since the volume of classified information about companies and private individuals, which is gathered and are stored in the local networks offices of state, hospitals and financial organizations, constantly it grows. Therefore the task of producing the rules, which would regulate transfer and exchange of the particular and corporate information of confidential nature, acquires special urgency.

Net technologies facilitate access to information, and it means, they make that with its more opened. Perhaps, one of the most fundamental achievements, which ensured the mass access of users to the local networks, became the propagation of the open structured cable systems (SCS). This, in turn, it led to the fact that simplicity of access to the data and wide acceptance of table computers and systems of storage of information reduced the level of safety and security of data.

Responsibility of state and organizations

In those regions, where the keeper of the classified information of particular, commercial or defense nature is state, its protection from the strangers is the task of the corresponding public bodies. The law of the European community about the protection of the rights of personality (Commonwealth Privacy Acts) accepted in 1988 lays on the state keepers of classified information responsibility for its safety. In the law, in particular, it is said: "... for the protection of information from the loss, the unsanctioned access, the use, the change or the promulgation, and also from other abuses must be accepted all measures, which be powerful to be considered reasonable for the present instance".

Some specialists assume that the requirements of protection SCS from interception fall outside the boundaries of reasonable. Their objections are reduced to the following. Certainly, any electronic equipment (except that specially designed) emits electromagnetic waves, but it is sufficiently difficult to register with its standard conditions, and if nevertheless this succeeds, then it will not easily use this information.

These objections could strongly cool interest in the problem of safety of the transmission of data along lines 10/100Base- T on the unshielded beaten pair (NVP), if not one unpleasant circumstance, discovered by the specialists of company Siemens - one of the most important German enterprises, which produce electronic equipment. In the course of experiments on the restoration of data on the basis of the readout of the emissions of the screen of computer, accepted at a distance of 100 m, they revealed that the maximum distance, at which was possible this interception, comprises more than two kilometers.

Responsibility for security and data security completely lies on developers, since requirements for the characteristics of cable system as a whole often exceed the requirements, presented to its individual parts. In spite of this, the majority of the developers of SCS and consultants continue to rely on the texts of standards and compose cable systems from the separate elements from different producers according to the principle "it collected and it included" (plug- Andes -play). In this situation it becomes especially important that those, who correspond for safety and security of information, would check the reliability of system as a whole, but its not individual parts.

Screened and unshielded systems

Although the cost of the unshielded cable (NVP) per one meter somewhat lower than cost of the screened beaten pair (EVP), the real savings, which ensures the selection NVP with the creation of typical local network, rarely exceeds several percentages. However, the value of expenditures - this only one side of problem.

Recent studies into the fields of safety of local networks, carried by many company- producers and state organizations, they showed the importance of the study of a whole series of the problems, which appear with the use NVP in the networks with the higher speed of transmissions of data. Such tasks include providing security and data security, study of its own radio-frequency emissions of the unshielded lines and their influence on the health of people.

An interception of dannykhy0/100Base- T, transferred by the unshielded line between the file- servers, the working stations and the printers, can be very easily carried out generally without any physical connection to the network, after establishing antenna not far from the cable. Everything which in that case will be required by that overhearing, the receiver of radio signals, electronics for their working and portable computer. The fact is that the cable - if only it is not ideally matched and loaded - is the transmitting antenna. The interception of the data thus is possible at a distance from several centimeters to several hundred it is meter, and in the majority of the cases to reveal the fact of the interception of data is completely impossible.

As a rule, by the local networks frequently are transferred the large volumes of data. For any, who attempts to illegally obtain information, network this is - present gift, since the time to the transfer of the large volumes of information became now substantially less. Furthermore, the unsanctioned hearing of networks with the frequency modulation (such as 10/100Base- T) also it is considerably simpler.

In order to ensure security and data security, transferred with the aid of protocols 10/100Base- T, many organizations come running to the technology of the coding of information in all cases, when by the local network are transmitted data, which require protection. If we do not encode given at least one time, then they can be intercepted, and therefore safety of further work of network can be set under the threat.

A drawback in the coding and decoding is the fact that these procedures absorb sufficiently many computational service lives of network. The installation of the expensive equipment in each node of network also can be required for them.

In addition to this, should be considered the significant administrative expenses, connected with the coding of data. Attempting to reduce the expenditures of time and resources, many users will unavoidably transfer by the networks and outside certain its quantity of data, which it should be encoded.

Version with the coding of data occurs much more expensive than the installation of the shielded cables. Furthermore, the coding of data can create in users a false feeling of safety. For the savings on the line with shielding it is necessary to pay with reduction in the useful operating speed of network and with expenditures for cipher equipment. But these expenditures can be at least estimated quantitatively. But damage, substituted to system as a result of the interception of information or actions of hackers to estimate much more difficult. Thus, the shielding of cables can be considered as the primary method of the protection of data, whereas coding - by second measure, necessary only sometimes.

However, simply the installation of the shielded cable it occurs insufficiently. All screened elements require the guarantee of a maximally possible degree of agreement; therefore screening must affect also coupling cables and joints. Besides this, with the installation EVP it is necessary thoroughly to follow the bending radii of cables and to attempt to minimize the spin-up of beaten pair for the installation of joints in order to preserve agreement between the beaten pairs after padding and connections of line.

Broadcasting local networks

If line with shielding are already established, then one should also care, also, about the reliable grounding of system. The rules of grounding are contained in recommendations ANSI EIA/TIA 607 and in the project of thus far yet not taken European standard prEN50174.

The correctly established screened cable system can significantly decrease the radiation level into the environment, which can be intercepted. Nevertheless, emission does not disappear at all, mainly, because of the presence in the network of active equipment.

The standards of American federal commission for connection (FCC) and European standard EU EN 55022 for the equipment of classes A and in, in which regulate the levels of electromagnetic radiations, the very low permissible radiation levels of equipment in the network are established. Analogously, for purposes of safety and protection of health, established the lowered radiation levels from the video devices. However, as a result of pursuit of the short-term economic benefit, this decrease in the radiation levels completely came on no because of the wide acceptance of networks on the base of the unshielded cable lines. Such networks emit into the surrounding space confidential data; for this they even was called from some chief analysts name the very caustic determination of "broadcasting local networks".