Exclusive The legal crackdown and publicity blitz aimed at people who share music, videos and software online may be having an unintended consequence for the troubled record industry. The number of file-sharers disguising their BitTorrent activity with encryption is skyrocketing.

Figures from a large UK ISP obtained by The Register show that the portion of BitTorrent traffic encrypted by file-sharers has risen 10-fold in the last 12 months, from four to 40 per cent.

This time last year, unencrypted torrents accounted for about 500Mbit/s of bandwidth, while files that had been scrambled by uploaders swallowed just 20Mbit/s.

The latest data shows that bandwidth used by unencrypted torrents has fallen to 350Mbit/s. Sharing of masked music, video and software has meanwhile exploded to average more than 200Mbit/s.

Matt Phillips, spokesman for UK record industry trade association the British Phonographic Institute, told The Reg : "Our internet investigations team, internet service providers and the police are well aware of encryption technology: it's been around for a long time and is commonplace in other areas of internet crime. It should come as no surprise that if people think they can hide illegal activity they will attempt to."

"When encryption is used to cloak torrent traffic it tends to be to hide something, and attracts greater attention for that reason. If certain ISPs are experiencing disproportionately high volumes of encrypted torrent traffic we expect it is partly in response to a combination of effective ISP abuse teams the enforcement efforts of the police and industry."

The last year has seen a significant escalation of the movie and music industry campaign against copyright infringement. The RIAA secured its first jury trial against Jammie Thomas, popular tracking site TorrentSpy was ordered to collect user data, and the supposedly private UK-based OiNK network was busted.

The file-sharing public's response has been revealed by analysis of data from deep packet inspection (DPI) technology, such as that made by Ellacoya and Cisco's P-Cube. Many ISPs, including BT here and Comcast in the US, have now deployed the kit to help throttle the amount of bandwidth consumed by P2P and other greedy net applications. Some BitTorrent encryption is certainly an effort to avoid such restrictions.

While DPI is able to identify and manage encrypted file-sharing packets, it is unable to look inside those packets for copyright infringement.

The trend towards encryption means current efforts by music publishers and government to cut a deal with ISPs to create a monitoring system to boot persistent copyright infringers off the internet, which we revealed last month is likely to be rendered pointless.