Mold remediation requires a cautious and diligent mitigation process that effectively removes the spores from the structure. Remediation is best left to certified professionals, since the most common approaches typically make the problem worse over time.
Mold spores are ubiquitous / virtually everywhere and tend to germinate in high moisture environments. Specific events, such as water leaking, flooding, or sustained high levels of humidity may provide ideal conditions for mold growth and promulgation.
Simply spraying bleach on mold is not a recommended remediation technique. When mold is treated with a chemical application or biocide, the spore will rupture or decay. During that process, the spore may release toxic sub-micron particles. When those particles are inhaled, they might exasperate and/or inflame allergies and/or health conditions.
A spray and wipe technique may be sufficient for tiny spot treatments upon smooth surfaces, such as a window sill. However, the same approach / treatment may make the problem worse when mold is widespread or embedded within porous surfaces. Spraying then wiping the mold may temporarily appear to work, but will likely aid the spread/ transmission of mold by effectively stirring the ruptured spores across wider surface areas while enabling spore to become airborne. Once airborne, the spores can be inhaled and attached to new surfaces where they may continue to spread.