First Nintendo DS Trojan
Source: Revo Europe

Reports have been spreading around of a trojan designed especially for the DS infecting some Japanese gamers. This trojan, when downloaded, deletes all the firmware programmed into the system, so the menu, clock, pictochat etc all will not be accessable. The trojan is said to be in the form of a hentai viewer, which allows the user to browse hentai material on the DS.

Currently no cures have been found for the virus. I believe if a person's DS unit was infected, perhaps Nintendo would be kind enough to reload the firmware back onto the system? Or maybe the firmware could even be downloaded off the net? I wouldn't know, but the next time you see someone complaining about a faulty DS console, you'll know they look at hentai :D.

Seriously though, this issue raises some concerns for the spreading of viruses on the DS. The first Wi-Fi game, Mario Kart DS will be released next month, so lets hope Nintendo will have some anti virus software guarding the Wi-Fi network. Currently, there are many homebrew programs available for the system, including homebrew games, GPS and Linux software etc. To be on the safe side, make sure you aren't downloading dodgey material, read some reviews on the program being using it :).