Virtual Private Networks (VPNs)

In Brief

The growth in Internet usage has given rise to new ways of working such as working from home, the exchange of classified information between different subsidiaries of the same company, and even viewing the websites and IT systems of suppliers or clients. As a consequence of this, a genuine security issue relating to these new methods of working is starting to emerge. 

‘Virtual Private Networks’ (VPNs) can provide an answer to some of these issues, and they are coming into increasing usage. The purpose of this article is to show the different types of VPN in existence and also to detail a few user scenarios.  


A virtual private network is a means of communication which ensures secure data transfer over public or shared networks (such as cable distribution and even ADSL). A VPN is, in fact, a communications network which uses the same security parameters as a private network. Its main features are:

  • data confidentiality: encryption guarantees that the content of data transmitted can only be known to the parties exchanging the information. Because of this, any third party intercepting VPN traffic will not be able to determine its content;
  • data integrity: cryptographic methods employed to ensure that the data received by the recipient over a VPN is identical to the data sent by the sender;
  • authentication of VPN users: it is important to know who is taking part in procedures to avoid security issues relating to identity theft and therefore illicit access to private networks.

VPN is a technology enabling a logical extension of a network or a sub-network of the organisation through the addition of workstations or sub-networks outside its physical boundaries. More specifically, employees working from home will be virtually acting within the internal network of the organisation, or between two remote sites or even a world apart, and sharing the same network.

Threats Encountered

The Internet provides no guarantees over the confidentiality or the integrity of data circulating over the web. For example, if you send an E-mail, it is entirely possible that a third party could intercept it, read it, and even alter some of the content.

This is unacceptable, especially concerning sensitive connections such as transactions with clients or partners or remote access to a company’s classified information (on a file server, for example).

The best means to counter such threats is currently the use of a VPN.


There are many different VPN protocols available and choosing the right one is not a simple matter. It is important to find out about the strength of the cryptographic algorithms being used. For example, the PPTP protocol – the protocol traditionally used in Windows infrastructures – is known to be no longer reliable because the authentication data can be stolen by third parties.

In general, the easiest thing to do is to use the type of VPN offered with the firewall solution of your organisation.

Security Policy

Draft and enforce the following sectoral policies: