Security :: Iptables State Module - Configuration Error / Not Enable Incoming Packets From Connections Initiated From Inside?
Mar 30, 2011
I have a server that I can only access via SSH (it's located far away) and I would like to secure it by blocking all ports except the ones that I need (which are HTTP and SSH). I still want to be able to make outgoing connections to enable software updates and other things.This is my iptables -L -n :
Code:
Chain INPUT (policy ACCEPT)
target prot opt source destination
ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED
DROP tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpts:1:21
DROP tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpts:23:79
DROP tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpts:81:65535
code....
In my opinion, this should block all incoming packets except the ones on port 80 and 22, but allow responses to outgoing connections. But a wget http://google.com does not work, it can't establish the connection.
Maybe this is not the best style for iptables rules, but I want to be absolutely sure to not accidently lock myself out from SSH, so I chose not to configure a "block-everything rule".
Does this configuration not enable incoming packets from connections initiated from inside?
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Apr 11, 2010
Its been really bugging me that whenever I scan my connection with wireshark I see this one person sending me a SYN packet every minute on port 445. I know this is the dangerous port that the Conficker worm travels along. So far my computer seems to be immune and I know, at least on the Linux side that I can just add a rule to my ip tables to block that port indefinitely. I want to know what the next step is.
00 0c 41 b2 e4 1d 00 11 09 b2 2f 0e 08 00 45 00
00 30 91 84 40 00 80 06 d1 c7 46 4f 86 29 XX XX
XX XX 10 43 01 bd 9e 23 d6 27 00 00 00 00 70 02
ff ff 65 58 00 00 02 04 05 b4 01 01 04 02
This is one of the packet captures I am getting. After sending me this and getting no reply, all of a sudden he goes up an ip. Basically this would be the pseudocode for what it looks like hes doing on my end.
while(1){
for(int i = 1; i != 255; i++){
send_connection_attempt("XX.XX.XX." + i);
}
}
To me this looks like this guy has hijacked a computer and is using it to run a script over. He is still scanning my network as I said earlier, what should I do? Should I contact my ISP? or just nail down the hatches and make sure nothing is exposed on my network?
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Apr 4, 2011
I'm trying to use iptables in order to forward all the incoming packets for port 5555 to port 5556 on the same server (192.168.2.101).
I wrote the following commands:
iptables -A PREROUTING -t nat -i any -p tcp --dport 5555 -j DNAT --to 192.168.2.101:5556
iptables -A FORWARD -p tcp -m state --state NEW -d 192.168.2.101 --dport 5556 -j ACCEPT
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Nov 25, 2010
I use iptables firewall (v1.4.1) installed on FC8. I'm trying to limit the inflow traffic for the port 1723 to certain MAC addresses. To experiment with the mac option, I've written the following iptables rule:
Quote:
iptables -A INPUT -m -mac --mac-source 10:08:08:08:08:10 -j ACCEPT
It didn't work. It gave me this error message:
Quote:
iptables v1.4.1: Couldn't load match `-mac':/usr/local/libexec/xtables/libipt_-mac.so: cannot open shared object file: No such file or directory
Try `iptables -h' or 'iptables --help' for more information. Does that mean the mac module wasn't installed/enabled?
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Apr 4, 2010
a good IPTABLES protocol to reject all incoming ssh trafiic except for a single IP or IP range?
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Apr 5, 2011
Can I, with only the use of IPTABLES, limit the incoming bandwith for a protocol? We have for example servers that have a FTP and HTTP server running and whenever HTTP has a lot of connections open, the other uploads/downloads get a timeout. I know I can limit the number of connections but prefer to limit on protocol level. Is this possible using IPTABLES and if so, can someone indicate how to proceed or provide a link? If it's not possible can someone point me to the right tool for the job?
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Apr 30, 2011
i dont know why packets dropped? and something else what are those numbers for default policy in [] means?this is rules:
Code:
# Generated by iptables-save v1.4.4 on Sun May 1 00:09:57 2011
*mangle
[code]....
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Jun 8, 2011
My VPS host a mail, blog and web site. So i want to block port i not use. The port that i use is 80,21,2022,443. The other port will be drop. I want to block bad packet and all packet that not related. Can anyone how to write in iptables?
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Jan 3, 2011
how can i drop igmp port 0 packets with iptables rule? my log file is full of this router advertisement.
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Apr 12, 2011
Here is my problem:
I need to enable the statistic module in iptables.
I had Fedora 13 32 bits, iptables-1.4.7-2 and kernel 2.6.18
But kernel 2.6.18 does not support statistic module.
So, I upgraded from Fedora 13 to Fedora 14.
Now I have Fedora release 14 (Laughlin) and Kernel 2.6.18
I did this to upgrade: url
Also, I did this too.
# yum update kernel
No Packages marked for Update
How can I ugrade to newer kernel?
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Jul 8, 2011
For some reason my FTP packets are blocked by iptables even though I thought I allowed them through
My syslog errors are along this line:
And my iptables ruleset:
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Jul 16, 2011
I have tried to configure my iptables to allow only HTTPS connections to the internet. Unfortunately, I didn't get that to work. I configured it like this:
Quote:
iptables -P INPUT DROP
iptables -P OUTPUT DROP
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A OUTPUT -t filter -p tcp --dport 53 -j ACCEPT
iptables -A OUTPUT -t filter -p udp --dport 53 -j ACCEPT
[Code]....
Of course I am only trying to access websites via HTTPS Still, I was wondering if HTTPS somehow under the hood requires the HTTP port to be open or if my rules are in some other way wrong.
ps: I got the rules from that website: [URL]
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Apr 7, 2011
I'm trying to adjust the firewall to only inbound syn connections.
To Allow all home subnets access to port 53 both tcp/udp but deny the rest.
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Jul 23, 2010
I'm having problems with hackers from across the globe trying to get into our servers. Why? i have no clue. nothing of value in my servers worth getting.
Right now my service only does business with USA. So I'm trying to find a way to block all Non USA traffic. I called my hosting provider and they are unable to help. Said it was up to me to do this.
Well I've already taken care of the TCP Wrappers. by spawning a small C program i made that uses MaxMind's GeoIP system. to automatically deny access. Now i need to do something about all the other network connections that come in to services that do not use the TCP wrappers.
So i was wondering if IPTABLES have a way to spawn a sub proccess like TCP wrappers or if there was any other firewall software out there for linux that would let me achieve my goal.
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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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May 14, 2011
I'm trying to limit the number of the ICMP packets reaching my server, so I'm using the limit module of iptables, unfortunately it seems the limit I set is totally ignored as I can easily send tens of ICMP packets and get a reply in less than 0.3 second Quote:
m3xican@m3xtop:~$ sudo ping -i0 -c20 x.x.x.x 20 packets transmitted, 20 received, 0% packet loss, time 230ms
rtt min/avg/max/mdev = 184.969/185.895/189.732/1.301 ms, pipe 16, ipg/ewma 12.138/186.232 ms This is the rule I'm using to accept ICMP packets (default setting is DROP)
Code:
iptables -A INPUT -p icmp -m limit --limit 1/s -j ACCEPT
And these are the kernel modules related to iptables
Code:
Module Size Used by
xt_limit 1382 0
[Code]...
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Nov 2, 2010
I am using a NanoStation 2 in Router mode.The NS is connected wirelessly to my neighbor's router and a switch is connect via ethernet to the NS for LAN use.
The past few days I'm trying to use a VoIP client software to connect to my VoIP account.I use Ekiga Softphone to do so, which requires UDP ports 3478-3479 and 5000-5100 to be open.
So I have opened these ports both on my neighbor's router and on the NS.The problem that I'm encountering is that although I manage to register to the VoIP service, when I answer an incoming call the caller is able to hear me, but I'm not able to hear the caller.So I used wireshark and figured that there is no incoming traffic on my end.
I have used many linux VoIP clients with PCs connecting straight forward to an ADSL router and worked perfectly.
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Apr 6, 2010
I have a router which makes two ppp connections. PPP0 is my default route and is an uncapped ADSL. PPP1 is a Local Only (South Africa) account which has DNS resolving to its IP. PPP1 allows certain connections in. I want all packets coming in on PPP1 to be marked so that after they have been routed through our local servers they can go back out over PPP1. Both connections use dynamically assigned ip addresses. I want to use PPP0 to make a connection to one of our stores, but when our stores connect to us they will be using PPP1. All packets from these incoming connections will need to be routed back over PPP1.
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Apr 3, 2009
I have computers in the DMZ (192.168.1.0/24) .. How to block traffic initiated from computers in the DMZ?
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Aug 9, 2010
I want each packet (that match iptables rule) to be delayed by some fixed time interval. How to to this?
Preudocode: iptables -A INPUT -p udp <more conditions> -j DELAY --delay 50000 # delay UDP packets for 50 milliseconds
Update: @related http://superuser.com/questions/147156/simulating-a-low-bandwidth-high-latency-network-connection-on-linux
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Oct 30, 2010
Pinging out from my netbook (over wifi, to any host) gets ~0% packet loss. Pinging into it (from any host) gets about 50% packet loss.
The router is a Dlink-DIR615 (rev d, running DD-WRT v24-sp2) but all other hosts on it ping eachother fine. I've tried changing routing, disabling IPv6, using older kernels and using wicd, all with no luck. The wireless connections is at 100% most of the time. This could be a new problem with Maverick, but I may not have noticed it before. I believe this is causing web browsing to be really slow and causing SSH timeouts.
I haven't tried madwifi drivers or nsidwrapper yet.
Edit: just booted into Windows and it has the same problem. Could it be a hardware issue? Also tried with a static IP, with no change.
Strangely, a normal ping gets 50% packet loss, but ping -A gets < 1% loss.
Edit 2: no packet loss at all on eth0.
Code:
# uname -a
Linux hulbert-laptop 2.6.35-23-generic #36-Ubuntu SMP Tue Oct 26 17:03:18 UTC 2010 i686 GNU/Linux
Code:
# ifconfig wlan0
wlan0 Link encap:Ethernet HWaddr 00:25:d3:1a:bc:4b
inet addr:192.168.0.102 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::225:d3ff:fe1a:bc4b/64 Scope:Link
[Code]....
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Dec 23, 2010
What is the best IPtables configuration for bind DNS server.
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Apr 4, 2010
I need some suggestions on software. I would like to offer remote desktop support to some of our clients, but some of them are using ISP's that block incoming connections so, VNC is out of the question. I was wondering if there is something similar to logmein for ubuntu?
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Apr 26, 2011
In December 2009 I switched my web-hosting package with 1and1 to their best VPS package. What a difference! At this time I knew absolutely NOTHING about Linux sys admin stuff. Now, I know a little more I now run 'several' VPS instances (all with 1and1). Back to the problem then... On all my boxes I run CentOS 5.5 (Linux 2.6.18-028stab070.4) with various different versions of Plesk (9.5.2 and 10.2.0) The VPS instances themselves are on Virtuozzo nodes. As you may know, Virtuozzo has a firewall GUI allowing modification of iptables. I only use this when I make a mistake and cannot SSH. My 'original' iptables: (the VZ chains are controlled by the Virtuozzo container)
Code:
Chain INPUT (policy DROP)
target prot opt source destination
VZ_INPUT all -- anywhere anywhere
Chain FORWARD (policy DROP)
[code]....
if this iptables chain limits the number of connections to 3 per second and 100 per second respectively, is this still secure or is there no point in having this rule? If the rule is a good one to have, then how can I allow http connections to bypass this chain/rule?
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Oct 24, 2009
incoming connections are not being reported to my /var/log/secure. I can't see if people are trying to connect. I can't troubleshoot because I can't do anything.
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Jul 19, 2011
I'm trying to get VNC working but I'm getting this error message:
Quote:
ssh: connect to host my_ip_address port 22: Connection refused
When typing:
Quote:
ssh -f -L 5900:localhost:5900 user@my_ip_address x11vnc -safer -localhost -nopw -once -display :0 && sleep 5 && vncviewer localhost:0
I'm trying to follow the instructions here: [URL] but I'm struggling with point 2 & 3:
Quote:
2. If you have previously reconfigured the firewall on your PC, make sure the firewall allows incoming connections on port 22 from anywhere, and on port 5900 from localhost (also known as 127.0.0.1)
3. If your PC is behind a home router, or any other device that uses NAT, configure your router to send connection attempts on port 22 (but not port 5900) to your PC
So my questions are:
1. I installed a fresh version of Ubuntu 11.4, should I be concerned about step 2? If so, how can I allow incoming connections on port 22 from anywhere, and on port 5900 from localhost?
2. Regarding step 3, I'm using NETGEAR model DGN1000 router. Is that something that I should do from the router's setting page or it's some commands that I should pass through SSH?
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Feb 24, 2010
I want to allow 100 incoming connections to my linux server running smtp. I know that tcpserver -c will set the limit of allowed incoming connections, but how can I tell what the currently set limit is?
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Jun 20, 2011
I'm trying to create and send my own ETH packets from inside the kernel.My objective to send the packages from layer 2 by building my own skbuffand sending itusingdev_queue_xmit().anyone did it or have examples of how to do it ?I tried to build my own skbuff without success.
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May 19, 2010
My question is simple - is there any linux app or applet which is able to show (monitor) incoming and outgoing connections assuming it's a direct internet access? I was using a firewall on a system off Redmont which was able to show every connection, listening ports of services if some were opened etc.
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Mar 13, 2010
I'm using Linux Mint 8 KDE, which is essentially kubuntu karmic.
Been trying to set up bittorrent (tried several different apps), have followed all the usual steps, forwarded ports on both Guarddog and my router, but still no incoming connections. Then tried disabling the firewall in Guarddog - still no incoming connections. Never had any problems configuring my router before so can only think that there must be something else blocking ports in linux other than iptables.Also had same problem just using ufw and gufw
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