German internet users face a 100-euro fine if they leave their wireless connection unsecured, following a ruling from the country's top criminal court.
The decision effectively outlaws open Wifi.
The ruling follows a lawsuit from a musician whose work was illegally downloaded and posted online - using an internet connection belonging to a man who was actually away on vacation at the time.
Despite this, the court ruled that the man was to an extent responsible for the download, as he hadn't done anything to prevent it.
"Private users are obliged to check whether their wireless connection is adequately secured to the danger of unauthorized third parties abusing it to commit copyright violation," said the court.
There's a limit to what the court expects - users don't have to have all the latest security installed, says AP. But they are now required to set up a password when they first install the system.
The country's consumer protection agency told the DAPD news agency it was reasonable to require users to install protection for their wireless connection. But it was fair of the court not to expect constant technical updates by private users, it said.