What materials will block or inhibit a magnetic field?
Almost any metal will partly screen a magnetic field by distorting its field lines. The effectiveness of the screening depends on a property of the metal called its magnetic permeability. An alloy called mu metal has one of the highest known magnetic permeabilities. A mu-metal box can reduce the field inside it by a factor which one web advertising page claimed could be up to a hundred thousand. This is useful for certain kinds of scientific experiments. Two boxes one inside the other should reduce the field to a completely undetectable value.
USB drives are the time-traveling fecal matter of silicon beings who exist 1 second in the future.
Most non ferrous metals will shield from magnetic fields. It normally only reduces it strength ,and does not eliminate it.
I don't know if some materials can block it, but you can cancel out magnetic field with opposing magnetic field. That's what coaxial cables do. Wire produce magnetic field around it, but coaxial cables cancel that out with covering up wire with conductive materials that carry electricity in opposite way.
as above. also, there is no iron in a usb drive. that would be be like wondering why a crab hasnt evolved into a moon yet.
