Deep packet inspection, frequently described as “drilling down” or “opening up the payload” to determine the actual content of a data packet, is the capability of looking at the content, rather than just the header, of data packets in transit on the internet. The capability, although it originally evolved for security reasons, opens the door to censorship and control of the flow of information on the net.

Ben Wagner, a graduate student in Political Science, Law, Statistics and International and Development Administration at the Ludwig-Maximilians University in Munich, Germany, and the University of Leiden in the Netherlands, has looked into the question of deep packet inspection and the implications that the spread of this technology has for censorship on the internet.

Deep Packet Inspection and Internet Censorship: International Convergence on an ‘Integrated Technology of Control’

Some excerpts:

… the link between deep packet inspection and internet censorship is of far greater concern for freedom of speech than its use in traffic shaping or preventing copyright infringement. At the present time many of the states censoring the internet are already known to use deep packet filtering.

DPI focuses on analyzing all the content of  data packets passing through the network, the headers and the data protocol structures (as opposed to the prior “Shallow Packet  Inspection” that would only analyze the packet header) and compares this content against rules or signatures (for example, virus signatures).

The use of DPI solutions has become so widespread that it is now used by many major global internet service providers. Furthermore, the use of DPI technology has become pervasive across the Internet, with most users frequently completely unaware of its existence.

When a packet is positively identified as matching a signature (a specific mixture of all of the above criteria) a wide variety of actions can be triggered. The most obvious example is to block the packet or disturb the entire internet connection. But simply removing the offending words, sentences or paragraphs is also possible, as is inserting other content into the packet or modifying large parts of it.

. . .

The actors using DPI can be broadly split into state and non-state actors. Generally speaking, non-state actors using DPI technology normally run large networks and see DPI as part of their network management. For state actors on the other hand the use of DPI is primarily of interest for security reasons.

As there is no significant divergence of interests between state and non-state actors, DPI technology will continue to spread throughout global Internet networks. This spread of DPI technology effectively provides the necessary foundations for the use of DPI as a censorship technology.

. . .

Despite the fact that deep packet inspection has been in use on the Internet for some time, it is now becoming widespread. There is still a great lack of awareness of the scale and capabilities of DPI on many levels, which has so far made meaningful policy debates about the technology difficult.

It is probably fair to say that a concept like network neutrality could go a long way to preventing censorship via DPI. However there is currently no agreed definition of what network neutrality is or could be and the distant idea of network neutrality as a ‘global norm’ is still some way off.

As one of the more measured contributors to the network neutrality debate has noted, “the strongest opposition [to Network Neutrality] is likely to come from […] and from national governments or third parties attempting to maintain their power to filter and censor the Internet.”

. . .

The two most common technical measures which are able to prevent deep packet inspection are encryption technology and non-textual frameworks. Whether their use will spread in response to the increased usage of DPI remains to be seen.

. . .

It is likely that the growing use of DPI within networks will have a significant impact on the development of the internet as a whole. Censorship is one of the most fundamental facts of the Internet in large parts of the world and is likely to be influenced by the spread of DPI.

Although network neutrality as a global norm is still some way off, a more open public policy debate might help define a framework in which an essentially generic technology such as DPI can be used without endangering freedom of speech or encouraging censorship.

And again, the original in PDF format is here:

Deep Packet Inspection and Internet Censorship: International Convergence on an ‘Integrated Technology of Control’