Back in November, Pocket-lint reported the news that law firm ACS:Law was planning to send out 15,000 letters to households that it suspected were sharing copyrighted material on the Web.

That campaign has just started to kick in, with letters now showing up, so to coincide a consumer rights group called BeingThreatened has put together a guide - the "Speculative Invoicing Handbook" - on to how to fight a false accusation for anyone who's been sent a nasty letter but didn't download or share the content in question.

"So far the unreliability of the evidence appears not to have been addressed", says James Bench from BeingThreatened. "100% of victims contacting BeingThreatened as a result of this new batch state they did not commit or authorise any copyright infringement of the work they are accused of sharing".

Many, including Conservative peer Lord Lucas, have criticized ACS:Law for its scattershot approach to the accusation letters. "I think most of their [ACS:Law's] income comes from people who just pay", he said, adding "I am not aware that there have been many court cases at the end of this because of the element of bluff".

So whether you know anything about filesharing, the Web, or P2P services or not, if you've been sent a letter demanding cash for copyright infringement and you didn't do it, then grab the handbook (PDF) - which has been published under the Creative Commons license and is free - and get reading.