Questions tagged [iptables]

An application that allows a user to configure the tables provided by the Linux firewall. iptables is succeeded by nftables as of 2014.

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MITM setup using airmon-ng, iptables, and isc-dhcp server

I want to set up a MITM-scenario as an exercise for myself. My setup looks like this: Internet <--------> Laptop <----------> Client At this stage I just want to route the traffic from my AP ...
1 vote
1 answer
670 views

Snort Inline Mode(IPS) Routing Packet Forwarding

I'd like to build an IPS which would be a seperate endpoint than the router and/or protected servers. To achieve this I've installed to my Ubuntu server Snort with DAQ(AFPACKET). The instructions I've ...
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Writing effective UFW & IpTable rules

I am quite new to UFW and IpTables and I am trying to understand what kind of rules we should look to implement to keep a web-application secure. The current scenario I am testing myself in is that I ...
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1 answer
167 views

UFW vs IpTables for web application security

I am trying to better understand measures that can be used to protect a web-application. I'm trying to determine which would be more effective, implementing a UFW or using IpTables. From my ...
1 vote
1 answer
466 views

Local Burp Proxy not showing routed packets

I created a hotspot on wlp2s0 and connected an android device, whose IP is 10.42.0.62. I am trying to route my all packets from my wlp2s0 interface to burp proxy which running on 8080 and I also ...
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TCP SYN/ACK on INPUT vs FORWARD

Are there any legitimate circumstances under which TCP SYN+ACK packets would arrive at a Linux firewall's INPUT chain, if it did not leave via the OUTPUT chain? That is, am I correct in assuming that ...
1 vote
1 answer
241 views

How do I differentiate a DDoS attack from a DoS attack?

My server is under attack on an specific port but I am confused whether is a DDoS attack or a DoS attack (if it requires a botnet or is using some kind of trick). The entire server is available (...
2 votes
2 answers
827 views

Is it safe to set up your firewall to allow localhost to accept incoming connections?

I have set up a VPN client and I'm using iptables to block all connections not tunneled through the VPN. An example of the iptables rules I am using can be found here. Unfortunately with this ...
21 votes
6 answers
4k views

Do machines without any listening services need a firewall to block incoming connections?

Let's assume we have an example machine connected to the internet. This machine is typically a client one, and it has no services like ssh running on. Does this kind of machines need any firewall to ...
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1 answer
435 views

How to block all inbound traffic from a specific Internet address or subnet using TomatoUSB router software (LINUX based)

I'm not trained in Linux, but I think I found the solution to my problem documented, but it is not working as expected. I am NOT an iptables guru, I'm learning as I go. A Russian IP is trying to ...
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1 answer
104 views

Why is the -L (list) option of iptables not available to non-root users?

Many tools in Linux allow for checking things as a non-root user. For example, at any time, I can check whether a service is running: $ systemctl status ntp However, the iptables needs to be used as ...
1 vote
1 answer
110 views

Is interface spoofing possible?

One commonly used iptables rule for Linux servers is this: # iptables -A INPUT -i lo -j ACCEPT Can we assume that this rule will only accept traffic which is sent from the local machine? Is it ...
1 vote
3 answers
232 views

How should I configure my firewall using iptables commands to defend against hacking? [closed]

I need to add extra security to my Android device using iptables and a firewall to defend against hackers. My specific goals are to prevent a hacker from remotely breaking into my device to begin with ...
1 vote
1 answer
139 views

Efficiently handling malicious, single connection attempts to a server?

I wanted to know what efficient way is there to handle malicious attempts to connect to my server by single IPs. The attempts show up logged in /var/log/auth.log as Connection closed by IPaddress port ...
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0 answers
136 views

Routing a site-to-site VPN through my regular VPN service

currently engaged in live competitive red vs blue team exercises in an enterprise style Windows AD environment. My device runs a modern Debian Linux OS. cscotun0 We typically connect to the lab/domain ...
6 votes
1 answer
3k views

ARP spoofing with Scapy. How does Scapy reroute traffic?

Background: I understand that in order to ARP spoof a victim in a network using Scapy, we need to send ARP reply packets to the victim and the gateway router with the correct destination and Source ...
1 vote
1 answer
583 views

Is it recommended to drop all traffic by default in iptables after accepting only what is required?

I was told using iptables -P OUTPUT DROP after rules such as iptables -A OUTPUT -p tcp --dport 80 -m state --state NEW -j ACCEPT to accept what is required didn’t do much from a security standpoint. ...
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What is the most restrictive way to allow IPv6 ICMP requests on iptables?

This is what I have so far but it is pretty open. *filter :INPUT DROP [0:0] :FORWARD DROP [0:0] :OUTPUT DROP [0:0] -A INPUT -p ipv6-icmp -j ACCEPT -A INPUT -i lo -j ACCEPT -A OUTPUT -p ipv6-icmp -j ...
0 votes
1 answer
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How do you securely give access to a Java App interactive console (Linux/GNU)?

I have a Java App running, which prints out messages into STDOUT and also has an active interactive console (also accepts STDIN), when the server has started up. How do I securely give access to an ...
6 votes
3 answers
7k views

What are the security implications of net.ipv4.conf.eth0.route_localnet=1 / route_localnet?

sudo sysctl -w net.ipv4.conf.eth0.route_localnet=1 What are the security implications of route_localnet?
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1 answer
203 views

iptables: force clients to use proxy

My network: 192.168.0.1 server. (enp0s3 NAT, enp0s8 internal) 192.168.0.10-15 clients (enp0s3 internal). I have a proxysquid for blocking websites,and so on. My clients can navigate and browse any ...
1 vote
2 answers
5k views

Block SYN,ACK response with iptables

I have a virtual environment and I am making a SYN flood attack to a Ubuntu Server's port 53 using Kali 2020. I realized that a countermeasure for this attack is to limit or block the responses to ...
3 votes
0 answers
137 views

smb iptables configuration not working with vpn killswitch

my main goal is to setup iptables that work as a VPN killswitch for my openvpn connection. Thanks to a post from forest, this was pretty straight forward: OpenVPN kill switch on Linux . So. everything ...
-1 votes
1 answer
161 views

Does this iptables entry indicate someone's trying to break in?

Two days ago I built a Debian 10 server in the United States for use as a file server for my web application. When I created the server, I installed the fail2ban package and configured a basic, ...
21 votes
2 answers
1k views

Fully transparent proxy

By default, mitmproxy will use its own local IP address for its server-side connections. What I want instead is mitmproxy to use the client’s IP address for server-side connections. The following ...
1 vote
4 answers
1k views

How to set iptables to drop packets that I'm not listening on?

I've got a Kali Linux box I use for pen testing. I would like to configure my machine to DROP incoming packets, but only when I'm not listening on them. e.g. if I run a netcat listener on port 80, I ...
2 votes
0 answers
876 views

TCP reset attack / forged TCP reset prevention

How do you prevent someone from doing an TCP reset attack between client and host without having acess to host? I am trying to solve a CTF for fun and learning purposes. In one of the challenges I ...
11 votes
1 answer
3k views

Has a remote rogue DNS client managed to slip through the first iptables rule of a Linux DNS server?

Ubuntu 20.04 iptables 1.8.4-1 I experienced a situation where a remote system seemed to be able to slip through the first iptables rule of a Linux server located behind a NAT router: -A INPUT -s <...
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1 answer
244 views

Why am I receiving hits with SPT=443 on IPv6?

I block most everything with my firewall, what I don't get is why would I constantly receive hits to connect on random ports from port 443. [iptables] reject_ipv6: IN=eno1 OUT= MAC=... SRC=2607:...
0 votes
1 answer
126 views

Even though my firewall is active, is it protecting me fully given that the 'rules' are not active?

Even though my firewall is active, is it protecting me fully given that the 'rules' are not active? Output shows: host based firewall active, empty rules iptables modules loaded, but no rules ...
0 votes
1 answer
4k views

Can't connect to fake AP with airbase-ng

I use kali-rolling on a virutal machine and I try to set up a fake access point using airbase-ng, but my devices won't connect to it whatsoever. My steps are: I put my wirless adapter in monitor mode ...
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2 answers
1k views

How does TLS traffic impact firewalls?

If I have an open port on a firewall it means that I can receive traffic on that port. If it's unencrypted I assume that the raw data is just allowed through. If TLS is being used, does firewall ...
2 votes
2 answers
262 views

How are my iptables rules circumvented?

I'm using ufw on a debian server and apparently an attacker is able to circumvent the filtering rules. ufw uses iptables. The server host http and mail services, and has an ssh port. I use a non-...
4 votes
2 answers
7k views

Why can't iptables drop arp requests

I was trying to hide my laptop from my phone's network scan app. The app is using arp requests to find devices on the network. I tried everything on iptables. It doesn't work, even if i set all the ...
5 votes
1 answer
885 views

SSL MITM on the WAN side of my router

Hi I would like to try to sniff a typical CWMP conversation that my router does to his Auto Configuration Server (see TR-069 crash course: https://www.iol.unh.edu/sites/default/files/knowledgebase/...
3 votes
0 answers
254 views

Experimenting with SSLStrip+ on the same machine

I am trying to play around to understand how SSLStrip+ works by: $ cat /proc/sys/net/ipv4/ip_forward 1 $ sudo iptables --flush $ sudo iptables --flush -t nat $ sudo iptables -t nat -A PREROUTING -p ...
12 votes
1 answer
29k views

Is it safe to disable connection tracking in iptables?

While reading about NOTRACK target of raw table in iptables, I encountered an article suggesting that for certain traffic you could (or even should) disable connection tracking. The two examples were: ...
1 vote
1 answer
1k views

watch DNS queries while using OpenVPN.-

I want to monitor/sniff the DNS queries I make while I'm using a VPN connection with my OpenVPN client. My initial motivation was to check if I'm leaking DNS queries; then using this page it seems I'm ...
13 votes
1 answer
17k views

Connection to ports 2000 and 5060 successful despite filtering

I run my own (Ubuntu based) router and have iptables configured to drop all incoming packets by default. To my surprise, running an nmap scan (from the WAN side) shows two open ports related to VOIP: ...
7 votes
4 answers
2k views

SIP UDP request breaking through iptables

I have been investigating a few instances recently where SIP UDP traffic has been somehow evading the ruleset defined in iptables leading me to suspect that there is a hole in our rules so i'm looking ...
5 votes
1 answer
267 views

System-Level Network Security (Packet Classification and etc.) - SELinux and Libnftnl

I read that Libnftnl is a userspace library providing a low-level netlink programming interface to the in-kernel nf_tables subsystem and it uses NFTables. Since it's a kernel related topic, at the ...
1 vote
0 answers
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Are parts of my system susceptible to IP based malicious attack even with effective IPtables rules?

Yesterday I installed Cent OS 6 and had to flush the default IPtables rules (IPtables -F) in order to access a web app via my browser. Having very little experience with Linux/Network security this ...
2 votes
2 answers
2k views

Dealing with the dangers of self-hosting a webserver?

Assuming for a self-hosted webserver: the webserver only hosts a static html website iptables is used to reject every IP except a few known ones only Port 443 is forwarded and the website requires ...
1 vote
1 answer
883 views

Building a malicious captive portal

So I'm trying to build a malicious captive portal but I'm stuck on the part where you need to know stuff. Anytime a HTTP request comes in, everything works fine. However, when an HTTPS connection ...
1 vote
1 answer
246 views

Is iptables and vpn tunneling enough? [closed]

What is the best approach to secure connection between two devices over the internet (public IP)? if there is a firewall on my public IP address deny access all incoming connection, can the hacker ...
2 votes
1 answer
100 views

What are the methods by which an attacker can distinguish between DROP on IPtables and a Nullroute or non-allocated IP?

Let's say we have a server set up with set to: iptables -P INPUT DROP Without any other rules on the input chain. Ignoring accessibility issues outside of physical server access, what are the ...
2 votes
1 answer
2k views

How to block traffic coming from an "public" WiFi hotspot and going to the LAN (iptables)

I followed this tutorial (http://elinux.org/RPI-Wireless-Hotspot) for an Wifi Hotspot in the guesthouse. This is working fine, but every device on the WiFi network can reach any LAN device in the LAN ...
1 vote
0 answers
164 views

Intercept data after sslstrip

I am able to use sslstrip successfully as shown here https://moxie.org/software/sslstrip/ What I want to do though is be able to use sslstrip with another proxy/script to modify requests/responses ...
1 vote
0 answers
323 views

Exploit vulnerabilty in embedded Linux network stack to disable iptables

I own a D-Link DCS-7110 HD POE network camera. It features an apparently iptables based access list configuration where you can allow/disallow certain networks and addresses from accessing the camera....
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0 answers
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IPSec and traffic mirroring [closed]

I have a VoIP server on which several SIP clients are connected to through IPSec tunnels. This is kind of an automated attendant so I both have RTP and SIP signalling flows. I need to be able to ...