Inthefieldsofphysicalsecurityandinformationsecurity,accesscontro

Inthefieldsofphysicalsecurityandinformationsecurity,accesscontrolistheselectiverestrictionofaccesstoaplaceorotherresource.Theactofaccessingmaymeanconsuming,entering,orusing.Permissiontoaccessaresourceiscalledauthorization(授权).Anaccesscontrolmechanism()betweenauser(oraprocessexecutingonbehalfofauser)andsystemresources,suchasapplications,operatingsystems,firewalls;routers,files,anddatabases.Thesystemmustfirstauthenticate(验证)auserseekingaccess.Typicallytheauthenticationfunctiondetermineswhethertheuseris(请作答此空)toaccessthesystematall.Thentheaccesscontrolfunctiondeterminesifthespecificrequestedaccessbythisuserispermitted.Asecurityadministratormaintainsanauthorizationdatabasethatspecifieswhattypeofaccesstowhichresourcesisallowedforthisuser.Theaccesscontrolfunctionconsultsthisdatabasetodeterminewhetherto()access.Anauditingfunctionmonitorsandkeepsarecordofuseraccessestosystemresources.Inpractice,anumberof()maycooperativelysharetheaccesscontrolfunction.AllOperatingsystemshaveatleastarudimentary(基本的).andinmanycasesaquiterobust,accesscontrolcomponent.Add-onsecuritypackagescanaddtothe()accesscontrolcapabilitiesoftheOS.Particularapplications.orutilities,suchasadatabasemanagementsystem,alsoincorporateaccesscontrolfunctions.Externaldevices,suchasfirewalls,canalsoprovideaccesscontrolservices.

A.denied

B.permitted

C.prohibited

D.rejected

正确答案是B