Virgin Media will trial deep packet inspection technology to measure the level of illegal filesharing on its network, but plans not to tell the customers whose traffic will be examined.

The system, CView, will be provided by Detica, a BAE subsidiary that specialises in large volume data collection and processing, and whose traditional customers are the intelligence agencies and law enforcement.

The trial will cover about 40 per cent of Virgin Media's network, a spokesman said, but those involved will not be informed. "It would be counter-productive because it doesn't affect customers directly," he said.

CView will operate at the centre of Virgin Media's network on aggregate traffic, the spokesman emphasised, and seek only to determine the proportion of filesharing traffic that infringes copyright.

The system will look at traffic and identify the peer-to-peer packets. In a step beyond how ISPs currently monitor their networks, it will then peer inside those packets and try to determine what is licensed and what is unlicensed, based on data provided by the record industry.

Virgin Media emphasised that it is seeking to measure the overall level of illegal filesharing, not to keep records on individual customers. Data on the level of copyright infringement will be aggregated and anonymised.

Nevertheless, the trial - which has no scheduled end date - is likely to prove controversial. CView's deep packet inspection is the same technology that powered Phorm's advertising system, which allowed monitoring and targeting of individual internet users. It too was trialled - by BT - without customers' consent or knowledge.

Detica is also understood to be in talks with other major ISPs with a view to wider trials of CView.

To begin with at least, Virgin Media's implementation will focus on music sharing. The ISP is preparing a legal download service in partnership with Universal, the largest of the four major record labels, which it hopes will be the "carrot" to Lord Mandelson's "stick" of technical measures against those who persistently infringe copyright.

"Understanding how consumer behaviour is changing will be an important requirement of Virgin Media's upcoming music offering and, should they become law, the Government's legislative proposals will also require measurement of the level of copyright infringement on ISPs' networks," said Jon James, Virgin Media's executive director of broadband.

As part of Lord Mandelson's "stick", the Digital Economy Bill, which the government is hoping to pass before the election, requires Ofcom to measure the effect of its anti-illegal filesharing provisions.

As we reported last week, Detica has also tried to pitch CView as an accurate method for regulators to use. At the launch of the Bill on Friday, however, a senior civil servant suggested that a crude estimate based on the level of illegal filesharing observed by rights holder organisations could be used.

In the pitch document, Detica said that as well as aggregate data, CView could be used to categorise filesharers and apply technical measures against them, or target them to be sold legal alternatives. Virgin Media's spokesman said it has no plans to use such features.

The Register will meet Detica executives next week to discuss CView. Post your questions about the system in comments. ®