I heard this and I want to do a global trade but the Pokemon might be glitched/hacked.
No,they are not.I have tried it myself.But there are some that are hacked like a lvl 5 Zekrom.So before trading,I would advise to see if it is legit.You can do this by seeing the OT and the lvl like the one given above.Also see if a Legendary Pokemon like Reshiram is a shiny,it most certainly is hacked.
Hope I helped!