Fedora Security :: Iptables To Deny All Except Localhost?
May 15, 2011
i was hoping that someone in here could possibly help me out with my iptables rule set. First here is what i would like iptables to do, i want iptables to deny all packets or traffic from the outside coming in and for output allow the things i need like web and irc etc... Also, i would like iptables to deny access to all services like sendmail and ssh except i would like localhost to have access to everything. What i mean by localhost is that when i run my iptables script it loads fine except when i try ssh from localhost i get this output:ssh -l user localhostssh_exchange_identification: Connection closed by remote hostI know what most of you are thinking, why do i need to ssh into localhost from localhost just open another terminal, well i am getting myself familiar with iptables i want all services logged and blocked but not from localhost. I cant seem to figure out this problem and i have tried several different things. Here is my iptables script, I am hoping that someone out there can tell me what i am doing wrong...
#!/bin/bash
iptables -v -F;
iptables -v -A INPUT -i lo -j ACCEPT;
I would like to know if it is possible to deny the access to a file for root? Would ACL's be a possibility? I have "googled" around but haven't found anything interesting (except SELinux). I should secure a password file to an important database.
I just downloaded the DenyHosts2.6python2.5.rpm for deny.hosts from sourceforge and would like to set it up. I normally use fish://, smb:// and ftp:// on the boxes on my lan. I already have files called hosts.allow and hosts.deny in the /etc folder. Will the rpm configure hosts.deny when first run?
I have an Asterisk on an externally hosted vServer with Lenny. In order to further protect the SSH access I intended to change the Port number 22 to something like 55555. For this I changed the /etc/ssh/sshd_config file and restarted ssh. This caused unfortunately the following problems:
(1) The first login works but DenyHost writes now the IP in its list so that the second login with the same IP is blocked.
(2) With RESET_ON_SUCCESS = yes several logins were possible with the same IP, but later it also was blocked for some still unknown reasons.
(3) Files can be uploaded for being edited, but they can't always be saved. When they can't be saved the next login with this IP is blocked. It thus looks like the blocking can occur while being connected. When the files can't be saved it is however still possible to copy files from the computer to the vServer.
I add below the entries in the auth.log from a logout and a login. It shows further how suddenly the attempts to save files were blocked. After this session the IP used for it was blocked. I don't know where the message "Unable to open env file: /etc/default/locale" comes from. If I remember right I had these messages already before. I don't know how much that is really important.
I'm having troubles trying to understand this problem:my homeserver until yesterday had a public IP, staying on network, with sshd running and all was fine;this evening I changed the IP, giving it a local lan address, and what happened if I tried to connect to it by ssh?I got an error about "Connection closed by remote host". Google helped me finding that was regarded to hosts.deny file, that was actually containing a lineALL:ALLthat I commented, and all was fine.My question is: why the hosts.deny (that has never changed) was observed only with the local IP?I tried to switch back to the public IP and leaving ALL:ALL, and it did connect without any problem
I have been struggling with this for a very long time now. I have installed Fedora Core 9 on my computer. I have set it up as a caching-nameserver and this is working.
Then I wanted to secure my server with iptables, and I have so far made this script:
# Load the connection tracker kernel module modprobe ip_conntrack iptables -F iptables -P INPUT DROP iptables -P FORWARD DROP
[Code]....
I can reach the dns server with ping. When trying Nslookup it says that it got SERVFAIL from 127.0.0.1 trying next server, and then it times out.
I am trying to do something outlandish with iptables (or so I think!).I have a source sending udp packets to a destination (say dst11). Using port mirroring I am able to get all these packets to a different machine (say dst22). I am able to see these packets on dst22 interface using tcpdump.I want to analyze the packets on dst22. So what I do is put dst22 interface in promiscuous mode (using ifconfig eth0 promisc). This in theory should get the packet through the MAC layer. Now using iptables I am trying to DNAT the packets in nat prerouting to change the packets destination IP to dst22's interface and change the destination port.
I made a Desktop User account. When I went on that account, it allowed me to execute sudo as if I was an administrator. I don't know what might be causing this. I do have ufw set up and blocking incoming connections. Do you guys know what might be at the root of this?Also, when I used sudo from the user account (which I shouldn't have been able to do), I provided the password for my admin account.
I just set up denyhosts and it worked properly the first time adding lots of ips to the hosts.deny.I then set it to run every 12 hours noon and midnight.I wanted to see if ran properly and I got all this.Does it look like its working?
I have a question, on my firewall at work I am seeing a constant flow of denies from many different source IP addresses, of tcp/udp destination port 53372 & 53375.What in the world is that, and why these two ports over and over
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.
i've got a few questions about iptables. i know how to set up ip tables to only allow from an ip address or a subnetting ip addresses. question is how do i allow from 2 different networks? would i need to create 2 lines of entry in iptables to the same port? e: allow 10.168.1.1 and 196.168.1.1 on port 22 is there a way to put all that in 1 line or would i need to create to rules for the port? i know i can use the ssh allow or deny but i'd like to stop access even before it gets to the ssh. stop it at the source kinda thing.
Wondering if anyone knows what the range specification is meant to do for the colonHAIN at the top of the iptables file? e.g. what is the 1:76 range mean for :OUTPUT ACCEPT [1:76] ?
# Generated by iptables-save v1.4.1.1 on Sat Dec 19 12:28:00 2009 *filter :INPUT ACCEPT [0:0]
I don't have a shell on FC12 with me to show the output of iptables -L -n but it looks good after above 2 commands. However, after issuing the following third command iptables -L -n gives "wrong" result
Namely iptables -L -n gives extra "/0" after 127.0.0.1 in the output I have checked on Ubuntu 9.10 and centos 5.4 and they don't give extra "/0"; iptables is not supposed to do that. Of course, I didn't invent these examples but they are abstracted from actual real life scenerio of trying to build rules on our servers.
I am using denyhosts on a server so in a config file/etc/denyhosts.confthe following value is setQuote:DENY_THRESHOLD_INVALID = 3which as per their configuration file saysQuote:
DENY_THRESHOLD_INVALID: block each host after the number of failed login # attempts has exceeded this value. This value applies to invalid # user login attempts (eg. non-existent user accounts)
i am learning security and firewalling. i want to know . where a linux firewall is sufficeint and where it is not sufficeint? if you can explain why or give a reference i will be glad. is that security or traffic handling problem? when i should select a cisco product? in tarms of traffic and sceutiry. do you have any good alternative recomendation to Cisco
I am using squid on my fedora box as a proxy server.By default the iptables (Firewall) service is on.To allow web pages to my client machines i stop the iptable service.
#service iptables stop
By doing it client computers start browsing.kindly how can I add a rule so that without stoping firewall client compter work fine.my perver IP address is 10.1.80.10
I've got two routers, 10.0.0.0/23 and 192.168.2.0/24, which are joined by a Linux box with interfaces eth0 (10.0.0.2) and ra0 (192.168.2.2). I've got masquerading for ra0, and a route to 192.168.2.0/24 on 10.0.0.0's router. I CAN ping hosts on 192.168.2.0 from 10.0.0.0 just fine, but I CANNOT access web pages.Strangely, If I enable masquerading on eth0, and add a route to 192.168.2.0s router to 10.0.0.0, I can ping AND access web pages from 192.168.2.0Here is my current iptables
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?
Let's say you have a host with some kind of locally installed root kit detector/scanner.
If someone managed to get root access to that box. Wouldn't the first thing to do, before installing a root kit, be to remove any kind root kit detector?
While investigating my localhost access logs during an investigation to resolve locking myself out of my own server(!) I noticed this recent access attempt from a proxy referrer. I wouldn't expect this on a local server - currently set to listen on 127.0.01. The request was 403 forbidden, but surely the request should not have even reached this far? Is this an example of an unauthorised access attempt? I don't think it is me because all of my usual access requests are in moz 5 and im logged in to linux currently.
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