The government's copyright division has issued a panic checklist for those receiving letters from US law firms demanding money for copyright infringement, warning that drive-by demands happen and that the claimant has to prove who was responsible before any guilt can be assumed.
The IPO seems to be worried that random firms might be firing in spurious claims, warning internet users: "If you didn’t know anything about the alleged copyright infringement check the letter is genuine. There are scams operating where letters are sent to try and gain compensation from you when you might not have to pay."
The full text also says users might want to check whether it was actually a child, a sofa-surfer, visiting relative or neighbour stealing the Wi-Fi who was actually responsible, adding: "It’s important to understand that the copyright owner can only take action against the person who actually committed the infringement. This may not be you. Your internet service provider (ISP) can only provide them with details of the internet account holder. Who may not be the actual infringer."
So don't buckle and pay anything unless you're 100 per cent sure it was you and you're feeling guilty, as the IPO finishes with: "It is the responsibility of the copyright owner to prove who has committed the infringement." [IPO via TorrentFreak]