Eicon Networks S92 Manual do Utilizador descarregar pdf (Página 68)

YuChakTinMichael‘sGIACGCFWProjectAssignment

Page 68

4. PropertiesmarkedBEFORELASTintheSecurityPolicyProperties

5. RuleBaselastrule

6. PropertiesmarkedLASTintheSecurityPolicyProperties

7. ImplicitDropRule

Onewaytocleartheconfusionistodisableallthepropertiesoptionsandbuildevery

rulefromscratch.Withinthecontextoftherulebase,sinceFireWall1examinesthe

RuleBasesequentially,rulesmustbecarefullyarrangedintheappropriateorderto

preventunwantedtrafficfromenteringthenetwork.

InGIAC’sexamplehere,thepolicyforEcommerce,EmailandDNSarenot

conflictingwitheachothers,sotheorderbetweenthemdoesnotmatter.However,

Rule4willdenyeverything,soitmustbeplacedatthebottom,ornothingwillbe

abletopassthroughthefirewall.

Infact,placingthemostfrequentlyencounteredrulesatthetopisgood

performancewide.However,forasmallandpreciserulebaseliketheonewehave

here,itreallydoesnotmatter.

Therearecertainspecialrulesthataretoberetained.Theserulesare:

n Stealthrule,whichispositionedasthefirstruleintherulebasetopreventtraffic

fromaccessingthefirewallitselfdirectly.

n Implicitdroprule,whichisaddedtothebottomoftheRuleBasebydefaultto

dropallcommunicationattemptsnotdescribedbytheotherrules.

RuleElements:

TodefinearuleintheFW1rulebase,thefollowingcomponentsmustfirstbe

defined:

n Source– thesourcenetworkobject(s)

n Destination –thedestinationnetworkobject(s)

n Service–theapplicationprotocol(s)

n Action –drop,accept,alert…etc

n InstallOn  thefirewallitself

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Eicon Networks S92 Manual do Utilizador Página 68