The white powder you see on brick, stucco, or stone is what is known as efflorescence. The white appearance is salt deposits that are left behind when water evaporates on porous surfaces. Efflorescence occurs naturally and is not the sign of a defect.
If you encounter efflorescence, it can be safely cleaned/removed with a mild solution of vinegar and water. You can also consider contacting a professional who may be offer more sophisticated treatments.