Kenzero is a computer trojan that is spread across peer-to-peer (P2P) networks and is programmed to blackmail its victims by collecting personal information and publishing their browsing history online in a public database.

The Kenzero trojan was first discovered by Symantec on November 27, 2009, but researchers believe it had spread undetected for a few months prior.

According to cybersecurity experts, Kenzero originated in Japan and is believed to be created by the same cybercriminal group behind the earlier trojan viruses Zeus and Koobface.

Kenzero attacks computers that download files through peer-to-peer (P2P) networks. A fake installation screen appears upon downloading an infected file, prompting victims to enter personal information. The virus then logs the victim's browsing history and publishes it online in a database. Finally, a dialog box or email is sent to the victim demanding a fee of approximately $16 USD for the removal of their browsing history from the database.

The virus hides inside video files of hentai anime and spreads via P2P file sharing networks.