...We've been infested!
Bugs are nasty little parasites that reside in nests, hidden away from sensor detection inside of domains. An inexperienced pilot without the proper equipment can easily find themselves walking right into one - that's when they attack!
Bugs are devious little machines that hack into the Digibeetle tanks that tamers use to traverse domains, sabotaging systems and causing all sorts of havoc. One can tell the type of damage a bug will do based on what type of shell the bug has. Some fill up your database's memory, steal energy off of the battery, constantly siphon out your money, and some can even dump Digimon out of your team! Best to avoid contact with Bugs at all cost!