Image caption The recipients are accused of infringing copyright by streaming porn

Thousands of Germans are reported to have been sent letters asking them to pay a fee for porn they are alleged to have streamed illegally online.

Law firm Urmann (U+C) is acting on behalf of Swiss copyright protection firm the Archive, and is asking for one-off payments of 250 euros (£210).

It confirmed to the BBC that the letters have been sent but would not say how many.

A growing number of affected people are claiming to be wrongly accused.

According to a German news site, more than 10,000 people are affected.

The German case is one of the first to target people accused of streaming rather than downloading pornography.

In this case U+C is targeting users who, they claim, have viewed content from porn-streaming site Redtube.

The law firm was unwilling to speak about its work to the BBC. Neither was the Archive available for comment.

In a twist, its campaign appears to have been taken up by cybercriminals who are sending out fake emails purporting to come from U+C but containing malicious software.

It led the law firm to issue a warning on its website urging people not to open the emails.

"Fake warnings on behalf of U+C have been sent by email. This email does not come from the law firm. Warnings on behalf of our clients are shipped exclusively by mail," it said.

Real evidence

The practice of law firms pursuing alleged copyright infringers has become a growing concern in recent years.

"In previous cases like this, we've seen some people pushed into paying up when they may have done nothing wrong," said Peter Bradwell of the Open Rights Group.

"It can seem more expensive or embarrassing to challenge the accusation.

"If a company wants to write to people it claims have infringed their copyright, a court needs to at least make sure the evidence they have is of a high standard and that letters being sent are fair and easy to understand."