▁V BR ▁and ▁the ▁backup ▁V BR .) ▁The ▁check sum ▁sector ▁is ▁a ▁check sum ▁of ▁the ▁previous ▁ 1 1 ▁se ctors , ▁with ▁the ▁exception ▁of ▁three ▁bytes ▁in ▁the ▁boot ▁sector ▁( Flags ▁and ▁percent ▁used ). ▁This ▁provides ▁integrity ▁of ▁the ▁V BR ▁by ▁determ ining ▁if ▁the ▁V BR ▁was ▁modified . ▁The ▁most ▁common ▁cause ▁could ▁be ▁a ▁boot ▁sector ▁virus , ▁but ▁this ▁would ▁also ▁catch ▁any ▁other ▁cor ruption ▁to ▁the ▁V BR . ▁A ▁second ▁check sum ▁is ▁used ▁for ▁the ▁up case ▁table . ▁This ▁is ▁a ▁static ▁table ▁and ▁should ▁never ▁change . ▁Any ▁cor ruption ▁in ▁the ▁table ▁could ▁prevent ▁files ▁from ▁being ▁located ▁because ▁this ▁table ▁is ▁used ▁to ▁convert ▁the ▁fil en ames ▁to ▁upper ▁case ▁when ▁searching ▁to ▁locate ▁a ▁file . ▁The ▁third ▁check sum ▁is ▁in ▁the ▁directory ▁file ▁sets . ▁Multiple ▁directory ▁records ▁are ▁used ▁to ▁define ▁a ▁single ▁file ▁and ▁this ▁is ▁called ▁a ▁file ▁set . ▁This ▁file ▁set ▁has ▁metadata ▁including ▁the ▁file ▁name , ▁time ▁st amps , ▁attributes , ▁address ▁of ▁first ▁cluster ▁location ▁of ▁the ▁data , ▁file ▁lengths , ▁and ▁the ▁file ▁name . ▁A ▁check sum ▁is ▁taken ▁over ▁the ▁entire ▁file ▁set ▁and ▁a ▁mismatch ▁would ▁occur ▁if ▁the ▁directory ▁file ▁set ▁was ▁accident ally ▁or ▁mal ici ously ▁changed . ▁When ▁the ▁file ▁system ▁is ▁mounted , ▁and ▁the ▁integrity ▁check ▁is ▁conducted , ▁these ▁hash es ▁are ▁verified . ▁Mount ing ▁also ▁includes