Use the Gufw fire­wall

APC Australia - - How to Linux -

EN­ABLE THE FIRE­WALL

Gufw is the graph­i­cal front-end for UFW, the un­com­pli­cated fire­wall, which is one of the sim­plest front-ends for ipt­a­bles. Fire up Gufw and change the Sta­tus tog­gle to ‘On’ to en­able the fire­wall. Gufw in­cludes three pro­files: pub­lic, of­fice and home. The de­fault is the home pro­file that de­nies all in­com­ing traf­fic and al­lows all out­go­ing traf­fic. This will let you surf the in­ter­net with­out any is­sues.

PRECONFIGURED RULES

Af­ter you’ve set the pol­icy for traf­fic, you can de­fine spe­cific rules for al­low­ing traf­fic for in­di­vid­ual apps and ser­vices. To cre­ate a rule, switch to the Rules tab and click on the ‘+’ but­ton. Use the Ap­pli­ca­tion pull-down in the Preconfigured tab to se­lect the app you want to al­low and Gufw will de­fine the most ef­fec­tive rule for that app. Then press the ‘Add’ but­ton to ap­pend the new rule.

MORE CUS­TOMI­SA­TION

The Ad­vanced tab is use­ful if you need to make minute cus­tomi­sa­tions as per your re­quire­ments — for ex­am­ple, if you only wish to al­low the SSH ser­vice from com­put­ers within a par­tic­u­lar IP ad­dress range over a par­tic­u­lar in­ter­face. Since the fire­wall matches traf­fic against rules in as­cend­ing or­der, you can also man­u­ally give your cus­tom rule a num­ber to spec­ify its po­si­tion in the list of fire­wall rules.

DE­FINE POLI­CIES

You can al­ter the in­com­ing and out­go­ing poli­cies by se­lect­ing one of the three op­tions in their re­spce­tive drop-downs. The Al­low op­tion will al­low traf­fic with­out ask­ing any ques­tions. The Deny op­tion will silently dis­card pack­ets, while the Re­ject op­tion also sends an er­ror packet to the sender. A good idea is to deny all in­com­ing con­nec­tions and then se­lec­tively en­able the ones you wish to al­low.

CUS­TOMISE RULES

Gufw en­ables you to tweak the de­fault rules, which comes in handy es­pe­cially when you’re run­ning a ser­vice on a non-de­fault port. Switch to the Sim­ple tab, which is sim­i­lar to the Preconfigured tab but in­stead of a drop-down list of apps, it al­lows you to man­u­ally spec­ify the port num­ber for the ser­vice. You can ei­ther add a spe­cific port (23) or a range of ports (11200:11299).

WATCH IN­COM­ING TRAF­FIC

One par­tic­u­larly use­ful fea­ture of Gufw is the live lis­ten­ing re­port. Af­ter you’ve added the rules, switch to the Re­port tab that’ll list all traf­fic along with other rel­e­vant in­for­ma­tion such as the pro­to­col, port, IP ad­dress and ap­pli­ca­tion. You can use this info to ad­just the rules par­tic­u­larly for in­com­ing traf­fic. Then there’s the Log tab which keeps track of Gufw’s ac­tiv­ity and helps iden­tify any sus­pi­cious ac­tiv­ity.

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