There was increased media attention last week for a London-based legal firm called ACS:Law, who proudly proclaim themselves to be "the only law firm in the UK actively pursuing through the civil courts identified copyright infringers on file sharing networks", ie they are overseeing legal action against suspected file-sharers akin to that pursued by the Recording Industry Association Of America for much of the last decade, and by the UK's BPI between 2003 and 2006.

It's not clear what content owners ACS represent, nor whether any of its clients are actually from the music industry, even though it cites 'music' as being one of its areas of expertise. It seems it sent out a stack of legal letters to suspected file-sharers last November, threatening to take said file-sharers to court unless they agreed to pay an out of court settlement, so similar to the infamous RIAA letters. A statement on the legal firm's website suggests that a second round of letters is due to be sent out anytime now to those who have failed to respond to their November correspondence.

The law firm is in the news because it has been singled out for criticism by consumer rights group Which? in its contribution to the file-sharing debate, and the copyright proposals in the government's Digital Economy Bill. They told reporters they had been approached by over 150 people who say they have been falsely accused of illegal file-sharing by ACS, and who were looking for advice as to how to respond to the legal letters they had received.

Which? quoted a letter from one such person, which perhaps gives us an indication of what companies ACS represents. It reads: "My 78 year old father yesterday received a letter demanding £500 for a porn file he is alleged to have downloaded. He doesn't even know what file-sharing or BitTorrent is so has certainly not done this himself or given anyone else permission to use his computer to do such a thing".

ACS's own website admits that it has "reviewed" some of the file-sharing actions it launched late last year and has decided to not proceed with any further action in some cases, possibly because of a lack of evidence of copyright infringement. Though the company's Andrew Crossley insists the methods for tracking file-sharing activity used by his clients are sound, and it seems that those net users who will not now be threatened with court action will still get a stern letter warning them to never file-share again. Meanwhile, the other actions launched last November continue to progress.

But Which? Technology Editor Matt Bath remains concerned about ACS's ongoing file-sharing litigation activities, telling the BBC: "Innocent consumers are being threatened with legal action for copyright infringements they not only haven't committed, but wouldn't know how to commit. Which? is concerned that many people will be frightened into paying up rather than facing the stress of a court battle". Especially, presumably, if the files they are accused of illegally downloaded are pornographic.

ACS have been subject to scrutiny by a number of consumer rights and pro-file-sharing groups ever since last summer, when they took over a number of file-sharing cases from better known London legal firm Davenport Lyons. Crossley insists that his legal activity in this domain is totally legitimate and fair, while also claiming that Which? have grossly exaggerated the total number of letters his firm have sent out to suspected file-sharers, which he says is under 500.