The most common type of DoS attacks result from Buffer Overflow vulnerabilities, which take advantage of discovered weaknesses within an operating system. For example, Microsoft security bulletin MS03-046, the "Vulnerability in Exchange Server Could Allow Arbitrary Code Execution" problem identifies how an attacker can cause a buffer overrun that could permit them to essentially hijack an organisation's email servers and run malicious programs in the security context of the SMTP service. Vulnerabilities of this kind are reported regularly; this is the 46th Microsoft Security Bulletin issued this year alone.

These threats can be thwarted by regular patching, but for the average organisation keeping up to date on all the patches released is time consuming and expensive. Add to that the plethora of different technologies required to protect the server, the chances are that the server will run into difficulties because other applications running on the same system are incompatible. This is a particular problem when Spam, Anti-Virus or content filtering solutions are implemented as 3rd party add-ons or plug-ins on a mail server. There is always a risk that a new security patch cannot be installed because of the presence of the 3rd party product or that installing the patch will stop the product from working. The system administrator is then faced stark with the choice of leaving a critical system unpatched or disabling a security product until an updated version can be supplied.

In the real world constant patching is not a practical solution and until recently many organisations have been prepared to take the risk and perform just a limited selection. However, with the time between vulnerabilities being announced to when they are exploited becoming increasingly shorter, the risks of not patching are becoming higher. Companies need to realise that email is too mission-critical to be afforded only limited protection and should start examining and evaluating their entire email security infrastructure.

What they will find is that many of the technologies they have implemented along the way are just stop-gaps, something that has worked well for the interim period, but now that they need to ensure sophisticated routing and delivery, provide users with remote access and still remain secure, these solutions are not enough. Spam may be hitting the headlines, but it is only part of the problem, there are many more issues impacting email that need to be addressed.


Email security is a complex problem that can only realistically be addressed with a specialist product. If the stability of the company's email flow rests in your hands, move on from spam, look at the bigger issues and save your bacon.



BorderWare Technologies are exhibiting at Infosecurity Europe 2004 which is Europe's number one IT Security Exhibition. Now in its 9th year, the show features Europe's most comprehensive FREE education programme, and over 200 exhibitors at the Grand Hall at Olympia from 27th to the 29th April 2004.