The battle between a mysterious hacker and Japanese police has taken a bizarre turn with the news that the authorities have recovered a memory card containing new clues sent to them strapped to a cat.

The card is reported by Japanese media as containing evidence that its sender was behind the ‘iesys.exe’ virus used by the hacker to anonymously send messages from remote PCs threatening to plant bombs in schools, including one attended by grandchildren of Japan’s Emperor Akihito.

Issued over several months in 2012, the threats explain why the police issued a reward of 3 million yen (about £21,400) for information leading to the individual’s capture, but the affair has also grown into a huge embarrassment for police.

In October it emerged that police has arrested and extracted confessions from four individuals whose PCs had apparently sent the threatening messages only for the real hacker to reveal that they had been hijacked using the ‘remote control virus’.

Failing to catch the culprit making the threats was bad enough but now the police were being exposed as willing to accept confessions from uninvolved individuals, probably using by coercion. The accused were released.

The widely reported cat incident has simply added to the growing feeling that the whole affair is a piece of cat and mouse theatre designed to expose the failings of investigators. If this was its purpose then it is succeeding.