Distributed　data　storage　systems　are　widely　used　to　store　data　with　the　development　of　big　data　and　cloud　computing.　Due　to　the　complicated　network　environment,　the　data　may　risk　being　destroyed　or　stolen　by　an　intentional　hacker.　In　order　to　mitigate　the　risk　of　data　destruction　and　data　theft,　this　paper　studies　the　joint　optimization　of　data　parts　allocation　and　computers　protections　to　defense　a　distributed　data　storage　system　in　order　to　maximize　the　system　reliability.　The　whole　data　is　divided　into　multiple　data　parts,　where　copies　of　each　part　can　be　made　and　allocated　onto　different　computers.　Two　different　cases　are　considered,　where　all　data　parts　on　a　computer　will　be　destroyed　in　the　first　case　and　all　data　parts　on　a　computer　will　not　only　be　destroyed　but　also　stolen　in　the　second　case,　if　the　computer　is　intruded　by　the　hacker.　The　system　is　reliable　if　the　defender　still　has　all　data　parts　and　the　hacker　does　not　obtain　all　data　parts.　For　both　cases,　the　system　reliability　is　evaluated　by　extending　the　universal　generating　function　technique.　Numerical　examples　are　carried　out　to　illustrate　the　applications.