2
votes
2answers
46 views

Are there ways to break into a machine if iptables drops all traffic?

Say I install Linux on an blank computer (no other OS, disk is formatted for installation), and I configure this in iptables: iptables -F iptables -P INPUT DROP iptables -P OUTPUT DROP iptables -P ...
0
votes
1answer
19 views

Simple iptables filter rule for 101/8 block not working

I run a webserver that caters to an entirely local crowd, so to keep hacking attempts to a minimum, I have inserted a bunch of international IP-blocking rules into my iptables, but my filters don't ...
1
vote
1answer
72 views

Is this what it looks like in the terminal on the client side when you are blocked out via fail2ban?

I am a new server admin. I just setup fail2ban on an ubuntu 12.04 VPS. I used this tutorial. Then I tried to login to the system via ssh from a friend's machine. It is showing "operation timed out." ...
3
votes
1answer
41 views

Did this tutorial block pings to my server?

I am a programmer teaching myself linux admin stuff. I followed this tutorial to setup a firewall on a VPS. As a part of that tutorial, I block all traffic except for web traffic and SSH traffic. I ...
0
votes
2answers
31 views

What is the default action for incoming packets that don't match explicit iptables rules?

CentOS 5.x I'd like to understand what is specifically happening to incoming packets that don't explicitly match rules in my iptables chains. Is the default action to reject them? Or drop them? ...
3
votes
1answer
44 views

How does iptables recognize packet state?

Consider these two sets of rules: Set A -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT -A INPUT -j REJECT -A OUTPUT -j ACCEPT Set B -A INPUT -m conntrack --ctstate ...
1
vote
1answer
243 views

How to Block SSH Brute Force via Iptables and How does it work?

I'm planning to add the following rules to iptables to stop ssh brute force attack which are common these days. -A INPUT -i eth0.103 -p tcp -m tcp --dport 4522 -m state --state NEW -m recent --set ...
1
vote
2answers
92 views

How is the loopback device traffic allowed?

How can I allow the traffic to be sent on the loopback device (lo)? What is the iptables command for it?
0
votes
1answer
143 views

iptables couldn't load target allow

I am using the command below to allow all traffic from hosts on my internal network but it says "iptables v1.4.18: Couldn't load target `ALLOW':No such file or directory". What is the problem here? ...
0
votes
1answer
107 views

iptables - why the stun, turn ports are not working to allow end points to access the server?

I have this iptables where all working except tcp/udp port 3478 and 5349. $ cat /etc/sysconfig/iptables # Generated by iptables-save v1.4.7 on Thu Nov 21 10:21:41 2013 *filter :FORWARD ACCEPT [0:0] ...
0
votes
0answers
420 views

Fail2ban - alternative robust for enterprise protection against DoS attack in SIP and similar to fail2ban features

Is there any fail2ban like software for CentOS 2.6.32-358.6.2.el6.x86_64 ? (fail2ban is 0.8.10 installed) but its slowing down the system completely, i was looking for something which can be similar ...
0
votes
1answer
119 views

Iptable rule to ssh over the internet

I've a server abc.example.com and a remote desktop zzz.example.com. I'm using SSH over a custom port, say, 6789. Whenever my firewall is off, I'm able to connect to the server successfully. But, as ...
1
vote
2answers
2k views

iptables blocking from internet side on eth1?

How to use iptables to deal with two Ethernet ports? eth0 port for LAN use (192.168.1.50 Private IP). eth1 port is connected to the internet via cable modem (80.0.xxx.xxx public IP). ifconfig ...
1
vote
0answers
103 views

Deny/allow a user's access to a port dynamically

I have stumbled upon this little tech dilemma yesterday, and know that there is a solution to it (IRC BNC resellers have it implemented already). However, the exact details and implementation elude ...
6
votes
2answers
3k views

Iptables: matching outgoing traffic with conntrack and owner. Works with strange drops

In my iptables script I have been experimenting with writing as finely grained rules as possible. I limit which users are allowed to use which services, partly for security and partly as a learning ...
1
vote
1answer
391 views

How to provide a “guest LAN” on one ethernet device

I have an always-on machine running Debian/Squeeze with a couple of ethernet ports (it's doing various serverish jobs, including DHCP) and a LAN on each. eth0 is on 192.168.7.* and has access to the ...
2
votes
2answers
444 views

Is xinetd still the best method to let non root daemons listen on privileged ports?

When I need to use SNMP monitoring for java applications, there is the need to that application (usually ran as daemon user) to listen on snmp port. If there is no other alternative, of course I can ...
1
vote
1answer
381 views

portsentry and IPTables on constant reboot, but not sure why

I have been doing some hardening on a new server [ centos 5.7 final ] i also have logwatch and seem to be getting these strange logs Commands Run: User root: /sbin/service portsentry restart ...
-1
votes
1answer
6k views

What is sport and dport?

I want to stop internet on my system using iptables so what should I do? iptables -A INPUT -p tcp --sport 80 -j DROP or iptables -A INPUT -p tcp --dport 80 -j DROP ?
2
votes
1answer
2k views

iptables rule to allow access to internet

I made default policy of my machine- iptables -A INPUT -j REJECT #DROP ALL PACKETS TO INPUT CHANNEL INPUT channel has been blocked. Now I want to allow only some specific services like I should be ...
6
votes
4answers
5k views

Fail2ban block with IPtables doesn't work on Debian Lenny. [moved ssh port]

I've recently decided to do some security maintenance. I saw my logs, and there were some tries against my SSH server. At first, I moved away the SSH port from the default 22. After it, I read ...
3
votes
1answer
171 views

Linux App that monitors log and add rules to iptables

I used to use a linux software that monitors logs like http, ssh, etc and if it detects that someone is trying to use brute force, it blocks that ip by adding a rule to iptables. I forgot what that ...
0
votes
2answers
137 views

Where to handle packets between clients?

"Server": 192.168.1.1 I want to "theoretically" disable that the clients can "ping" each other. Can i use an iptables rule for it? e.g.: iptables -A FORWARD -m iprange --src-range ...
3
votes
1answer
202 views

Is there a standard way to configure what policy iptables loads on startup under Debian?

I've just started playing with Debian 6.0 (Squeeze) in a VPS environment, as a way to learn more about system administration. One thing I'd like to configure is a default packet filtering policy. ...