Mystery Datas are objects in the Net that contains random objects such as Battle Chips, Bug Frags, or Zenny. Either that or a Virus Battle can be triggered at random if viruses are disguised by Green Mystery Data. This could be prevented with the SubChip "UnTrap".
The most common Mystery Data which can be found in the Net, computers, or enemy computers. Every time Megaman jacks out of the computer, they reappear. Their contents contain not limited to small amount of Zenny, a Battlechip, or a small amount of BugFrag.
From BN4 onwards, there are Green Mystery Data in battle. If the player finishes the battle with the GMD intact, they will get a reward in addition to their battle results. Otherwise, no extra reward.
Can be found anywhere. The BMD is located in a preset location and cannot be aquired again once the player gets the BMD the first time. The contents of it can be HP Memory, Rare Battlechips, or even Navi Customizer programs.
In enemy computers, they are there to unlock doors or such.
Could be found in Net Areas, requires the SubChip "Unlocker" to open. It's contents are much greater than Blue Mystery Data, resulting very, very rare Battle Chips.
- Gold Mystery Data: (BN6 Only)
The rarest of all of Mystery Data, one could not simply get that easily as they have 20% chance of finding those on the Net. However, they could be opened like GMD and contains vast amounts of Zenny, BugFrags, or a rare Battle Chip.