Ubuntu Security :: Delete Builtin Ufw Rules / Block The FTP Ports?
May 6, 2011
How do you delete ufw rules which you didn't make?
I want to block the FTP ports (20 & 21) but even if I put in DENY rules, it appears that these rules are letting traffic through
Code:
9 400 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:20
0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 multiport dports 21,20 state RELATED,ESTABLISHED
0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 multiport dports 21,20 state RELATED,ESTABLISHED
How do I delete these rules? I've tried.
Code:
sudo ufw delete allow 20
sudo ufw delete proto tcp from any to any 20
but I get "Could not delete non-existent rule".
Since I didn't make those rules I have no idea what OpenBSD's PF syntax (what ufw uses) is for them.
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May 2, 2010
my ufw rules have been loaded and active yet using iptraf i see tcp connections on ports that were never allowed by ufw. can anyone explain this too me does ufw just not work?
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Jun 30, 2010
I enabled ufw yesterday, and am finding log entries like:
Jun 30 13:07:51 xxxx kernel: [15702368.296557] [UFW BLOCK] IN=eth1 OUT= MAC=00:22:19:5e:8f:23:00:0c:db:fc:8b:00:08:00 SRC=xx.xx.xx.xx DST=xx.xx.xx.xx LEN=40 TOS=0x00 PREC=0x00 TTL=55 ID=47632 PROTO=TCP SPT=58875 DPT=80 WINDOW=65535 RES=0x00 ACK FIN URGP=0
What is puzzling is I did the command: ufw allow 80.
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Jan 20, 2010
how to block all ports except pop,pop3,smtp in nat using iptables in squid on redhat A3
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May 1, 2010
I have trouble with opensuse susefirewall 2 and my own rules. since i have installed a suspicious download manager, i detect outgoing traffic in the monitor and i want to block ougoing traffic except some apps like firefox, jinchess ...
1) I had to modify FW_CUSTOMRULES="" with FW_CUSTOMRULES="/etc/sysconfig/scripts/SuSEfirewall2-custom" in /etc/sysconfig/SuSefirewall2
2) I had to add my own rules in /etc/sysconfig/scripts/SuSEfirewall2-custom in the appropriate hook
3) I don't know if rules are good.. they seem to work because for example jinchess can't access his server with the DROP rule until i add the ACCEPT rule BUT in fact the download manager still access internet and amarok too when it searches for songs lyrics ! i have discovered it's because the others apps use port 80
I give here the file /etc/sysconfig/scripts/SuSEfirewall2-custom
How to to make firefox use another specified port ? i wanted to use privoxy with tor but it doesn't work .. is there input/output controler on linux (something like zonealarm on XP) ? the trouble is that all outgoing traffic is permitted by default!
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Aug 3, 2010
I have been trying to figure this out for a long time now and can't seem to get it to work. I have three serial ports I need to communicate with. The first one works, but the other two, which have identical product and vendor IDs, do not. This is what I have so far under /etc/udev/rules.d/10-local.rules/
[Code]....
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Dec 16, 2010
I was following the directions over on the page How to watch Hulu overseas without a proxy server and got to the section about blocking ports, which I need to block port 1935. I figured this would be easy, as the mac instructions are
Code:
sudo ipfw add 0 deny tcp from any to any 1935
sudo ipfw add 0 deny udp from any to any 1935
and the Windows instructions are practically a book in itself. Since this page was lacking instructions on how to do it in Ubuntu, and ipfw seemingly doesn't exist in Ubuntu, how do I block the ports
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May 12, 2011
I need assistance with my Snort Installation. I used Bodhi Zazen's Network Intrusion Detection System post and found it easier than the previous time I had done it. I am currently running Ubuntu 10.04 server and Snort 2.8.6.1 with BASE 1.4.5. I followed Bodhi Zazen's instructions and when I tested snort it ended with a Fatal Error due to ERROR: /etc/snort/rules/exploit.rules(264) => 'fast_pattern' does not take an argument
Fatal Error, Quitting.. Here is the entire output once I ran the test command: snort -c /etc/snort/snort.con -T Running in Test mode
[Code]...
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Jun 25, 2010
I have a Suse 10.3 router with 4 network cards. 1 is to connect to the big network and thereby also the internet, 2 are for 'client' subnets and I want to use the last one as a DMZ. In this DMZ will be a web server which has to be accessible from the other 2 subnets and from the big network. I could do it with a few simple clicks in Yast firewall, but I have some issues with this firewall and there for I want to use it as minimal as possible, using Iptables.
So now I'm struggling a bit with Iptables. Basicly what I'm looking for is how to block all ports but 80 in this last subnet with iptables.
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Jun 15, 2010
How can I block all ports except
ssh (port 22)
httpd (port 80)
using iptables and iphains?
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Sep 9, 2010
can i actually edit /etc/sysconfig/iptables and create/delete rules inside that file?will it work? i just find using the IPTABLES -A or -D command a hassle
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Jun 9, 2010
I googled this question, no relevant results. I don't samba, ssh, or any P2P file sharing. Is udp neccesary for general web browsing/file downloading? What would be the best general ufw rules to set for above conditions and varying ip address? I know how to use the full ufw syntax in command line.
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May 9, 2010
I have a set of iptables rules generated by Firestarter, and i'm in the process of trying to familiarise myself with iptables itself, but there's one particular rule which is confusing me, perhaps somebody could explain it to me
My INPUT chain reads as follows:
Code:
Chain INPUT (policy DROP)
target prot opt source destination
ACCEPT tcp -- cdns01.plus.net anywhere tcp flags:!FIN,SYN,RST,ACK/SYN
ACCEPT udp -- cdns01.plus.net anywhere
ACCEPT tcp -- cdns02.plus.net anywhere tcp flags:!FIN,SYN,RST,ACK/SYN
[Code]...
Given that the firewall is actually blocking packets, it can't be this simple, so what am I missing?
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Sep 12, 2010
I've configured iptables to act as a stateful firewall, but instead of simply rejecting packets I'd like to waste a potenial hackers time by droping any packet that would otherwise be returned. Are my rules sufficient or have I somehow opened myself up to an attacker by trying to write these rules myself?
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Jul 9, 2011
what do the following two commands do? Do they modify the iptables rules in any way?
sudo /sbin/iptables -L -n
sudo /sbin/ip6tables -L -n
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May 30, 2010
When I upgraded to 10.4LT I agreed to something that stopped snort, after days decided to just re-do with new snort version. Used bodhi.zazen's MySql instruction version (which is what I used in the past) Everything went pretty well except for figuring out that I needed to delete all the lib_sfdynamic_preprocessor_example?? files (I also deleted all the lib_sfdynamic_example?? files too just to be safe). Used my original Oinkmaster with updated rules version and downloaded the emerging threats too (as I had in the past) and snort won't run with some of the emerging threat rules because it's lookning for snortsam (fwsam). I read up and snortsam looks like a good idea (if I'm wrong somebody just let me know)
if this seems dumb, but I really don't understand, the snortsam directions are HORRIBLE, the snortsam src looks like a windows file when unpacked with all the .dll files(but they say for all OS's), it builds but you need to copy the binary to /usr/local/bin (what in ubuntu would be a binary?).
the snortsam-patch-2.8.tar.gz won't unpack and the Snort 2.8.6 patch is a file, not a package (have no clue where to put it or what to call it if I got the 2.8.tar.gz to unpack so I could build it)
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Jun 22, 2011
I recently set up a ftp server in my house running a dyndns service so I can get to it from the outside. I called my isp to get some help in setting up the router to forward port 21 from the outside to that box, and in short we had some problems. Long story short, they ended up bypassing the router itself, and now the line running to the box is its own fixed external ip. Naturally I want a pretty darn good iptables setup for this. The box runs proftpd and so far my iptables only accepts local loopback and port-21. (I left port 80 closed as its only purpose is to be a standalone ftp server) But I know there must be a safer rule for port 21, as right now its just wide open. Anyone have any ideas on how to make this a bit safer? Also would that command be fine for any of the linux machines im connecting to it from the outside too?
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Dec 21, 2010
on a fresh Fedora 2.6.35.9-64.fc14.x86_64 installation I have little trouble with chrony. I love that tool for synchronyzing my clock. SELinux complains, that /usr/sbin/chronyd like to read/write to chronyd.pid. Further I find entries in /var/log/messages, that /var/lib/chrony/drift could not be opened. As I'm completely new to SELinux - I'd like to get some help setting the Security Rules. PS: Should the rules be quite fine from the FC-Repo?
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Jan 27, 2011
I have a caching dns and SNMP ( MRTG ) both on the same server how can I permit dns and snmp traffic in INPUT chain?? I have tried the following:
iptables -A INPUT -p udp --sport 1024:65535 --dport 53 -j ACCEPT
iptables -A INPUT -p udp --sport 53 --dport 1024:65535 -j ACCEPT
iptables -A INPUT -p udp --sport 1024:65535 --dport 161:162 -j ACCEPT
iptables -A INPUT -p udp --sport 161:162 --dport 1024:65535 -j ACCEPT
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Sep 16, 2010
I am trying to program iptable rules for implementing a 1:1 NAT which does the following:
1. Forward all traffic from all ports on a public ip to a private ip
2. Forward traffic from a range of ports (x-->y) on a public ip, to a private ip
I did some google searches for the same, and came up with the following.
iptables -A FORWARD -t filter -o eth0 -m state
state NEW,ESTABLISHED,RELATED -j ACCEPT
iptables -A FORWARD -t filter -i eth0 -m state
state ESTABLISHED,RELATED -j ACCEPT
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Mar 31, 2011
Can someone please let me know strong iptables rules? Below entries are in iptables file.Here Y.Y.Y.Y is another branch public IP.This server acts as gateway+squid server.Further it will serve company's intranet page also using httpd.OS is CentOS 5.0.
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Jan 27, 2011
I am setting my firewall rules using the command iptables.My question is i wanna know what command i can use that list rule 2 and 3 for instance in my table?i want to create rule that: The host is administered using SSH, scp and sftp so allow incoming SSH traffic and securing remote file copying and transferring.
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May 3, 2009
When I use system-config-firewall, it asks what interfaces to trust. Where does it store that information for iptables (or whatever uses that info)? How iptables knows at what interfaces to use the rules?There is not that kind of information in /etc/sysconf/iptables and iptables-config.
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Jul 16, 2011
I don't know if FC15 has the iptable rules like the ones shown below by default or not but I wanted a second opinion about the safety they provide. Why is icmp accepted (INPUT rule 1) from/to all ip? and is it better to remove this rule? When the protocol is all (INPUT rule 2), does it mean from ip layer and above?? and is it required/safe to have this rule? The 3rd rule is to allow tcp-port 22 connections (ssh) to/from all ip. I think this is correctly set and required. The 4th rule in INPUT table rejects pings with the icmp-host-prohibited message; which I don't think is the best solution. Instead it can be set to silently drop icmp packets. Then, the FORWARD table uses reject instead of silent drop for forwarding icmp ping packets.
Code:
what do you think about the new rules and their order?
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Mar 10, 2011
I need with some iptables rules. I've done all I can, Googling all over, to cover as many exploits as possible and the following script is what I've come up with. The current set up works and I've checked with NMAP. I just need some sort of confirmation that this is pretty much what I can do.
Code:
LAN="eth0 eth1"
RANGE=10.1.0.0/17
WAN=eth2
# Delete all existing rules
[code]....
Also, if I wanted a broadcast to be relayed to all subnets within a defined range, how would such a iptables rule look like? I need this in order to find a networked Canon MP640 printer.
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Aug 25, 2010
I put together the following filter set :
Code:
#!/bin/sh
#To understand this script, reference the No Starch Press Linux Firewalls Book.
MODPROBE=/sbin/modprobe
IPT=/sbin/iptables
IPTSV=/sbin/iptables-save
IPT6=/sbin/ip6tables
IPT6SV=/sbin/ip6tables-save
### flush / drop policy sets
echo "[+] Flushing existing rules with DEFAULT of DROP [+]"
echo "[+] IPv4 [+]"
$IPT -F
$IPT -F -t nat
$IPT -X
$IPT -P INPUT DROP
$IPT -P OUTPUT DROP
$IPT -P FORWARD DROP
echo "[+] IPv6 [+]"
$IPT6 -F
$IPT6 -F -t nat
$IPT6 -X
$IPT6 -P INPUT DROP
$IPT6 -P OUTPUT DROP
$IPT6 -P FORWARD DROP .....
###OUTPUT rules: LOG rule
$IPT -A OUTPUT -o ! lo -j LOG --log-prefix "DROPED OUTBOUND" --log-ip-options --log-tcp-options
I wanted to know how to allow certain applications through the outbound tables. For example, I wish to be able to use tools such as nmap,tracepath, and traceroute. However, I am not sure where to look to understand the ports to open. I was starting to think that maybe rather than ports to open it would need to be somehthing like tcp flags that would ned to be allowed. Any way, I have tried google and am still haing problems. I started wanting to use these tools due to getting ready for my network+ and security+ certs.
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Feb 22, 2011
I'm trying to set up a firewall at the moment that allows access to my custom SSH port from only my friend's url (they have a static url but dynamic IP). I find iptables a bit of a nightmare and was hoping to use UFW for most of my day to day firewall maintenance and just make a few extra iptable rules to cover exceptional circumstances like this. Fortunately it seems UFW allows this with /etc/ufw/before.rules and /etc/ufw/after.rules. So at the moment I'm just trying to get the basic iptables rules right. As I say I'm not very good with iptables, does this look right?
Code:
## Drop Default SSH port access With Logging
iptables -N SSH_DEFAULT
iptables -A INPUT -p tcp --dport 22 -m state --state NEW -j SSH_DEFAULT
[code].....
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Jul 11, 2010
so the firewall rules I am currently using are displayed below.
Code:
# DROP ALL FORWARDED PACKETS
iptables -P FORWARD DROP # DROP ALL PACKETS
# ALLOW DHCP THROUGH THE FIREWALL
[code]....
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Jul 19, 2010
I have been trying to figure out how to makes rules in iptables that expire after a certain amount of time. From what I have found online you want to use the recent module with --rcheck and --seconds. I have found a few examples and have given them a shot but I can't seem to get it right. Would anyone mind posting an example of a rule that will auto expire?
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Feb 20, 2010
I've configured squid proxy server in a P4 desktop. I've 50 users in my network. I installed RHEL 4.4 (2.6.9-42 kernel) and the iptables version is 1.2.11-3.1. I've 2 NICs installed in the system. eth0 (192.168.100.99) for local lan and eth1 (192.168.1.2) for outgoing to internet. I've connected DSL broadband modem to eth1 (default ip of DSL modem is 192.168.1.1). All the clients except few has been forced to go through squid by user authentication to access internet. Those clients which were kept away from proxy are 192.168.100.253, 192.168.100.97, 192.168.100.95 and 192.168.100.165. Everything works fine but from last week I observed that one of some notorious user use the direct IPs (192.168.100.97 or 192.168.100.95) in the absense of the owner of these IPs to gain access to internet as we applied download/upload restrictions in squid.
I want to filter the packets of source hosts using MAC address in PREROUTING chain. I read somewhere that IPT_MAC module must be installed to make this happen. So that those notorious users can not change their ips to gain direct access to internet.
Below are the contents of my iptables file (I've ommited few entries for safty purpose).
# Generated by iptables-save v1.2.11 on Wed Nov 25 16:35:57 2009
*filter
:INPUT ACCEPT [14274:3846787]
:FORWARD ACCEPT [4460:1241297]
:OUTPUT ACCEPT [16825:4872475]
code....
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