A Trojan circulating in Japan seeks to extort money from shame-faced fans of hentai-themed games.

Those who download illegal copies of ”over 18″ hentai-themed games from file sharing networks are liable to wind up with a nasty surprise, Trend Micro warns.

Some bogus files posing as games from Abel software attempt to trick victims into handing over personal information as part of a supposed game registration process. Meanwhile, in the background, the malware is collecting information on the victim's computer including domain, OS version, file use history and IE favourites.

Screenshots from a prospective mark's PC are also obtained. This data is then published on a publicly-viewable website before victims receive an email pointing them towards the incriminating content from Romancing Inc, which also maintains the domain hosting the incriminating data.

The email offers to resolve the “copyright infringement” and remove incriminating (and potentially embarrassing) information in exchange for a fee.

Trend Micro notes that the Trojan forming the centrepiece of the attack drops MP3 files on a victim's machine that are elsewhere offered for sale online at an extortionate price of hundreds of thousands of dollars.

Security researcher Rik Ferguson writes: "Could it be that once a victim has shown themselves to be extortion-friendly they will get hit with yet another 'copyright infringement' notice from Romancing Inc? Japanese copyright law was strengthened this year largely in an attempt to address the problem of illegal downloading.

"This is certainly another illustration of why, in the long run, you may well be better off paying up front for your downloads and steering clear of file-sharing networks."

Previous scams along the same lines have claimed to be FBI notices of copyright infringement. The Hentai-themed ruse goes further by publicly shaming prospective marks before hitting them with extortionate demands.

More on the web-based smut shakedown can be found in a blog posting by Trend Micro here. ®