▁fashion , ▁for ▁example , ▁as ▁PHP ▁web ▁pages . ▁ ▁Such ▁front - ends , ▁gener ators ▁and ▁scripts ▁are ▁often ▁limited ▁by ▁their ▁built - in ▁template ▁systems ▁and ▁where ▁the ▁templates ▁offer ▁substitution ▁sp ots ▁for ▁user - defined ▁rules . ▁Also , ▁the ▁generated ▁rules ▁are ▁generally ▁not ▁optimized ▁for ▁the ▁particular ▁firewall ing ▁effect ▁the ▁user ▁wishes , ▁as ▁doing ▁so ▁will ▁likely ▁increase ▁the ▁maintenance ▁cost ▁for ▁the ▁developer . ▁Users ▁who ▁reason ably ▁understand ▁i pt ables ▁and ▁want ▁their ▁rules et ▁optimized ▁are ▁ad vised ▁to ▁construct ▁their ▁own ▁rules et . ▁ ▁Other ▁notable ▁tools ▁ ▁Fire H OL ▁– ▁a ▁shell ▁script ▁wrapping ▁i pt ables ▁with ▁an ▁easy - to - under stand ▁plain - text ▁configuration ▁file ▁ ▁Nu F W ▁– ▁an ▁authentic ating ▁firewall ▁extension ▁to ▁Net filter ▁ ▁Sh ore wall ▁– ▁a ▁gateway / fire wall ▁configuration ▁tool , ▁making ▁it ▁possible ▁to ▁use ▁easier ▁rules ▁and ▁have ▁them ▁mapped ▁to ▁i pt ables ▁ ▁See ▁also ▁▁ ▁N PF ▁( fire wall ) ▁ ▁P F ▁( fire wall ) ▁ ▁i pf ire wall ▁( ip fw ) ▁ ▁ip filter ▁ ▁X DP ▁ ▁ip ch ains ▁ ▁References ▁ ▁Liter ature ▁ ▁External ▁links ▁▁ ▁The ▁net filter / ipt ables ▁project ▁Web ▁page ▁▁▁ ▁The ▁net filter / ipt ables ▁documentation ▁page ▁( out dated ) ▁ ▁Det ect ing ▁and ▁dece iving ▁network ▁sc ans ▁counter me asures ▁against ▁n map