It's a sitcom that launched long before today's world of internet piracy, smartphone addiction and one laptop per child.

But Friends is still popular with web-savvy copyright infringers – and Warner Brothers is not letting them off lightly.

Friends was big in 1995. Twenty years later pirates have capitalised on that popularity.

Or is it?

Piracy news website TorrentFreak has obtained a letter the studio sent to someone who allegedly pirated season two, episode five of Friends, in which it asked the individual to cough up *ahem* $US20 in compensation, or risk being sued for copyright infringement.