
YuChakTinMichael‘sGIACGCFWProjectAssignment
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DesignPrinciple
AsmentionedbyLanceSpitznerinhisarticle“BuildingYourFirewallRulebase”,
securitypolicydefineswhatistobeenforced
2
.
Thefirewallisatoolfordefininghowthesecuritypolicyisenforced.Beforewe
implementanyfirewallsolution,thesecuritypolicymustfirstbeclearlydefined.As
Lancesaid,thekeytosuccessissimplicity.Complicatedpolicygivesroomto
misconfiguration.
Firewallrulebasesfollowandimplementthedefinedsecuritypolicies.Forevery
rulebase,theprincipleisstraightforward–anythingnotexplicitlyallowedbyaruleis
rejectedbydefault.Thiswaytherulebasecanbekeptassimpleaspossiblewithout
theneedtointroducetonsofcomplicated(andpossiblyconflicting)rules.
Layered Architecture
Itisnotpossibletoencompassprotectionofallsortsforeverysegmentintoasingle
firewall.TheGIAC’snetworkdeploysalayeredprotectionarchitecture,meaning
differentfirewallsareimplementedatdifferentpointsofthenetwork.Theentire
networkissecuredwhentheappropriatesecuritypoliciesareallocatedtothe
appropriatefirewallsuchthateverycornerofthenetworkissecured.
Toimplementthissecurityarchitecture,weneedto:
1. defineoverallsecuritypoliciesfortheenterprisebasedonitstechnical
requirements
2. allocateenforcementdutiestothefirewalls
3. oneveryfirewall,definespecificrulesandsettingsforpolicyenforcement
2
http://www.enteract.com/~lspitz/rules.html
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