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B
