https://www.youtube.com/watch?v=h5Igc18hc2Qthe first video here is the virus itself. it spreads by starting a trade with someone at the cable club. the infected host starts a trade with the victim, and when it starts, the virus spreads by uploading its save to the victim's cartridge.
once uploaded, both systems return to the title, and the save has spread to the other cartridge. booting the save reveals that you are trapped in the same area as the host, in front of the cable link NPC with no way to escape. however, you are given an inventory item that allows you to change any pokemon in your box. this could possibly be used on the 3DS's Pokemon Box, as the save can be put onto a 3DS via homebrew tools and allow you to use the virus's inventory item feature.
however, on a gbc/gb, you are trapped, with your only method of power being to spread the virus and entrap other unsuspecting players.
https://www.youtube.com/watch?v=Ny1b_Lwg0xkand onto the second. the same creator also "made" an antivirus. by defeating gym leader sabrina, you obtain it (it's actually just a bug/error -- it won't run the exploit from the host if certain flags are set). when the virus attempts to spread, the entire system shuts off, preventing its ability to spread and leaving the original savedata intact.
overall i thought this was really neat and a rather awesome way of programming new things onto such an old game/console/system. i love these kinda things.
edit: oh and by the way some of us are talking about homebrew so feel free to chime in
i'll make a homebrew general l8r
