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Groups > linux.debian.user > #167034

Firewall - basic config?

From Harris Paltrowitz <harrisupstate@yahoo.com>
Newsgroups linux.debian.user
Subject Firewall - basic config?
Date 2016-04-23 19:10 +0200
Message-ID <rr9ea-6Ge-9@gated-at.bofh.it> (permalink)
Organization linux.* mail to news gateway

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Hi List,

I have a question regarding how I've configured my iptables to act as a 
very basic "firewall", i.e., one that simply prevents any and all 
incoming connections.  Now, from my readings over the past several days 
I think I've learned that at least some of my outgoing requests will 
have responses that should be allowed to come back in -- but aside from 
that, I essentially want my firewall to act in a very "default" method, 
i.e., the way a complete neophyte would expect his or her firewall to 
work within Windows or Mac.

Here's what I did -- I will also paste the results of my current 
"iptables -L" command...  I hope the text block is not too large...

1. First, my issue with manually configuring iptables is not the 
complexity of it, per se -- but the fact that I want to avoid having my 
newness to it prevent me from setting it up in an insecure manner.  So...

2. I found that "ufw" works as a line-command-based-front-end to 
iptables.  I also came across "gufw" in my travels, and I even tried it, 
but I've since gleaned that all that's really needed in ufw to 
completely mimic the basic functionality of gufw is to (a) install ufw, 
and (b) enable it -- one does not even need to establish the default 
policies, although the Debian wiki page incorrectly states that this is 
necessary.

3. So after having installed and enabled ufw, here's the output of my 
"iptables -L" command.  I noticed a mention of "microsoft-ds" in 
there...  I assume this is just a protocol, and not a piece of 
software!  Any suggestions/comments would be much appreciated. Thanks 
very much.

Chain INPUT (policy DROP)
target     prot opt source               destination
ufw-before-logging-input  all  --  anywhere anywhere
ufw-before-input  all  --  anywhere             anywhere
ufw-after-input  all  --  anywhere             anywhere
ufw-after-logging-input  all  --  anywhere anywhere
ufw-reject-input  all  --  anywhere             anywhere
ufw-track-input  all  --  anywhere             anywhere

Chain FORWARD (policy DROP)
target     prot opt source               destination
ufw-before-logging-forward  all  --  anywhere anywhere
ufw-before-forward  all  --  anywhere anywhere
ufw-after-forward  all  --  anywhere             anywhere
ufw-after-logging-forward  all  --  anywhere anywhere
ufw-reject-forward  all  --  anywhere anywhere

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination
ufw-before-logging-output  all  --  anywhere anywhere
ufw-before-output  all  --  anywhere             anywhere
ufw-after-output  all  --  anywhere             anywhere
ufw-after-logging-output  all  --  anywhere anywhere
ufw-reject-output  all  --  anywhere             anywhere
ufw-track-output  all  --  anywhere             anywhere

Chain ufw-after-forward (1 references)
target     prot opt source               destination

Chain ufw-after-input (1 references)
target     prot opt source               destination
ufw-skip-to-policy-input  udp  --  anywhere anywhere             udp 
dpt:netbios-ns
ufw-skip-to-policy-input  udp  --  anywhere anywhere             udp 
dpt:netbios-dgm
ufw-skip-to-policy-input  tcp  --  anywhere anywhere             tcp 
dpt:netbios-ssn
ufw-skip-to-policy-input  tcp  --  anywhere anywhere             tcp 
dpt:microsoft-ds
ufw-skip-to-policy-input  udp  --  anywhere anywhere             udp 
dpt:bootps
ufw-skip-to-policy-input  udp  --  anywhere anywhere             udp 
dpt:bootpc
ufw-skip-to-policy-input  all  --  anywhere anywhere             
ADDRTYPE match dst-type BROADCAST

Chain ufw-after-logging-forward (1 references)
target     prot opt source               destination
LOG        all  --  anywhere             anywhere             limit: avg 
3/min burst 10 LOG level warning prefix "[UFW BLOCK] "

Chain ufw-after-logging-input (1 references)
target     prot opt source               destination
LOG        all  --  anywhere             anywhere             limit: avg 
3/min burst 10 LOG level warning prefix "[UFW BLOCK] "

Chain ufw-after-logging-output (1 references)
target     prot opt source               destination

Chain ufw-after-output (1 references)
target     prot opt source               destination

Chain ufw-before-forward (1 references)
target     prot opt source               destination
ufw-user-forward  all  --  anywhere             anywhere

Chain ufw-before-input (1 references)
target     prot opt source               destination
ACCEPT     all  --  anywhere             anywhere
ACCEPT     all  --  anywhere             anywhere             state 
RELATED,ESTABLISHED
ufw-logging-deny  all  --  anywhere             anywhere state INVALID
DROP       all  --  anywhere             anywhere             state INVALID
ACCEPT     icmp --  anywhere             anywhere             icmp 
destination-unreachable
ACCEPT     icmp --  anywhere             anywhere             icmp 
source-quench
ACCEPT     icmp --  anywhere             anywhere             icmp 
time-exceeded
ACCEPT     icmp --  anywhere             anywhere             icmp 
parameter-problem
ACCEPT     icmp --  anywhere             anywhere             icmp 
echo-request
ACCEPT     udp  --  anywhere             anywhere             udp 
spt:bootps dpt:bootpc
ufw-not-local  all  --  anywhere             anywhere
ACCEPT     udp  --  anywhere             224.0.0.251          udp dpt:mdns
ACCEPT     udp  --  anywhere             239.255.255.250      udp dpt:1900
ufw-user-input  all  --  anywhere             anywhere

Chain ufw-before-logging-forward (1 references)
target     prot opt source               destination

Chain ufw-before-logging-input (1 references)
target     prot opt source               destination

Chain ufw-before-logging-output (1 references)
target     prot opt source               destination

Chain ufw-before-output (1 references)
target     prot opt source               destination
ACCEPT     all  --  anywhere             anywhere
ACCEPT     all  --  anywhere             anywhere             state 
RELATED,ESTABLISHED
ufw-user-output  all  --  anywhere             anywhere

Chain ufw-logging-allow (0 references)
target     prot opt source               destination
LOG        all  --  anywhere             anywhere             limit: avg 
3/min burst 10 LOG level warning prefix "[UFW ALLOW] "

Chain ufw-logging-deny (2 references)
target     prot opt source               destination
RETURN     all  --  anywhere             anywhere             state 
INVALID limit: avg 3/min burst 10
LOG        all  --  anywhere             anywhere             limit: avg 
3/min burst 10 LOG level warning prefix "[UFW BLOCK] "

Chain ufw-not-local (1 references)
target     prot opt source               destination
RETURN     all  --  anywhere             anywhere ADDRTYPE match 
dst-type LOCAL
RETURN     all  --  anywhere             anywhere ADDRTYPE match 
dst-type MULTICAST
RETURN     all  --  anywhere             anywhere ADDRTYPE match 
dst-type BROADCAST
ufw-logging-deny  all  --  anywhere             anywhere limit: avg 
3/min burst 10
DROP       all  --  anywhere             anywhere

Chain ufw-reject-forward (1 references)
target     prot opt source               destination

Chain ufw-reject-input (1 references)
target     prot opt source               destination

Chain ufw-reject-output (1 references)
target     prot opt source               destination

Chain ufw-skip-to-policy-forward (0 references)
target     prot opt source               destination
DROP       all  --  anywhere             anywhere

Chain ufw-skip-to-policy-input (7 references)
target     prot opt source               destination
DROP       all  --  anywhere             anywhere

Chain ufw-skip-to-policy-output (0 references)
target     prot opt source               destination
ACCEPT     all  --  anywhere             anywhere

Chain ufw-track-input (1 references)
target     prot opt source               destination

Chain ufw-track-output (1 references)
target     prot opt source               destination
ACCEPT     tcp  --  anywhere             anywhere             state NEW
ACCEPT     udp  --  anywhere             anywhere             state NEW

Chain ufw-user-forward (1 references)
target     prot opt source               destination

Chain ufw-user-input (1 references)
target     prot opt source               destination

Chain ufw-user-limit (0 references)
target     prot opt source               destination
LOG        all  --  anywhere             anywhere             limit: avg 
3/min burst 5 LOG level warning prefix "[UFW LIMIT BLOCK] "
REJECT     all  --  anywhere             anywhere reject-with 
icmp-port-unreachable

Chain ufw-user-limit-accept (0 references)
target     prot opt source               destination
ACCEPT     all  --  anywhere             anywhere

Chain ufw-user-logging-forward (0 references)
target     prot opt source               destination

Chain ufw-user-logging-input (0 references)
target     prot opt source               destination

Chain ufw-user-logging-output (0 references)
target     prot opt source               destination

Chain ufw-user-output (1 references)
target     prot opt source               destination

-end of posting

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Thread

Firewall - basic config? Harris Paltrowitz <harrisupstate@yahoo.com> - 2016-04-23 19:10 +0200
  Re: Firewall - basic config? Reco <recoverym4n@gmail.com> - 2016-04-23 20:10 +0200
    Re: Firewall - basic config? Michael Milliman <michael.e.milliman@gmail.com> - 2016-04-24 07:20 +0200
      Re: Firewall - basic config? Reco <recoverym4n@gmail.com> - 2016-04-24 11:00 +0200
        Re: Firewall - basic config? Michael Milliman <michael.e.milliman@gmail.com> - 2016-04-26 04:10 +0200
  Re: Firewall - basic config? Joe <joe@jretrading.com> - 2016-04-23 22:00 +0200
    Re: Firewall - basic config? shawn wilson <ag4ve.us@gmail.com> - 2016-04-25 15:50 +0200
  Re: Firewall - basic config? cbannister@slingshot.co.nz - 2016-04-27 10:40 +0200
  Re: Firewall - basic config? Jonathan Dowland <jmtd@debian.org> - 2016-04-27 11:30 +0200
    Re: Firewall - basic config? Harris Paltrowitz <harrisupstate@yahoo.com> - 2016-04-27 13:50 +0200

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