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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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6
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2answers
5k views

How web application firewalls protect application from DDoS attacks?

How to protect a web application from DDoS by the implementation of Web Application firewalls? How effective is this method?
3
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3answers
948 views

Make OSSEC ban ip on remote firewall

I am deploying OSSEC architecture agent-server mode. I want the server to ban ip not only on agent but also on a remote firewall (dedicated iptables server). I've seached on the OSSEC's ...
1
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1answer
258 views

Security implications of packets with an invalid state (iptables)

I have been seeing few rules with -m state --state NEW, ESTABLISHED, RELATED. First I thought that was pointless as it was contemplating the three possible states, so there was no need to define -m ...
0
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1answer
667 views

Can an attacker detect if I have a TARPIT enabled?

Last thing we want to do is provoke an attacker and offer them challenges or puzzles indirectly to give them a flag to stay and continue to hack rather than move on to other hosts. If possible, I do ...
2
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4answers
5k views

Logging server compromised (IptabLes and IptabLex)

I am trying to figure out how it was compromised. They installed IptabLes and IptabLex in /boot. They also added /etc/init.d/IptabLes and /etc/init.d/IptabLex which simply call the respective /boot ...
3
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1answer
174 views

Is it possible to find out what a remote user is trying to do connecting to a closed port?

From my iptables log, I can observe a particular remote IP address trying to connect to my server from port 80 to a private port number: Jul 09 01:24:41 example.com kernel: IPTABLES: IN=eth1 MAC=xx:...
0
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1answer
76 views

Utility of Output Chains in IPTABLES when there is no Network Firewall— Is it ok to permit all outgoing connections from a server?

I have a set of INPUT chain rules restricting traffic based on source ip and destination ports.The services are ftp and a job service.The server has a public ip address. The default policy of the ...
0
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1answer
2k views

Block specific packets/sequences of packets to remove disturbing client “feature”

Recently, one of my client-server application started to disturb me with some very annoying "notifications". Basically, what happens is that the remote server sends a few packets to my client, which ...
4
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4answers
1k views

Find out what Linux software is trying to phone home

I have seen some suspicious outbound communications blocked on my VPS, which hosts a small experimental Web site, and want to find out which application is making the attempt. The server is running ...
0
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3answers
928 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 ...
3
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2answers
3k views

Is my ISP doing a port scan on my computer?

I have been logging incoming connections with iptables for a while and I have been observing the following popping up periodically: 11:45:10 my.com kernel: IPTABLES: SRC=220.255.XX.XXY DST=192.168.1....
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1answer
401 views

Allow loopback in Iptables?

I'm trying to write Iptables rules for a small web server. Almost every source I've encountered recommends to allow loopback access to the web server, but doesn't explain why this is necessary. What'...
3
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1answer
2k views

ufw, system-config-firewall-tui, or firewalld vs iptables

Is there any advantage (other than usability) to using ufw, system-config-firewall-tui, or firewalld rather than just using iptables? My understanding is that these other programs just simplify ...
1
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0answers
57 views

How to manage security for multiple PC and VM?

I have a firewall VM which creates I have used to setup subnet for different purposes. For example: (fake ips, of course) 1.1.2.1/24 DMZ 1.1.3.1/24 Internal 1.1.5.1/24 security/logging I use ...
2
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2answers
621 views

Isolating guest networks

I'm setting up a secondary guest wifi on my router and I want to make sure that it's impossible for clients connected to the guest wifi to access my primary network. Initially, I used IP filtering ...
0
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2answers
941 views

Does iptables work in kernel mode? [closed]

I am not sure about that. It should run in kernel mode in order to avoid some user-mode program to kill/suspend the firewall and do its dirty job. The malware would not be able to kill the firewall ...
0
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1answer
448 views

How does a website get pass my server firewall and attempt to hotlink to my server resources?

I was stumped when I saw the following lines on my Apache server error log this morning: [authz_core:error] [client ::1:37317] AH01630: client denied by server configuration: /var/www/styles/...
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0answers
662 views

forcing a traffic redirect?

I am trying to get my machines to be force through a MiTM and the MiTM to redirect them to a server of my choice (which happens to be the MiTM on port 17002) I am running ip tables: sudo iptables -t ...
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1answer
2k views

Bridge Firewall vs Routing Firewall

What is the difference between bridge and routing firewall ? How they both works and what are the security advantages/disadvantages for both scenario ?
2
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2answers
437 views

Are there “LAN IPs” on the internet?

I have a home-made web application and thought that an easy way to secure it's administration interface would be to simply reject all IPs that arent from 192.168... Is this viable? is it possible for ...
1
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0answers
526 views

Throttling DropBox behind a firewall

Our office network bandwidth gets choked when an employee copies a large file into her DropBox, since it gets downloaded on several machines (of other employees). LAN Sync is an option, but needs to ...
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2answers
216 views

How secure is a Windows PC that is routed through a Linux PC?

I have a Dual PC setup. Two PC's are networked together via crossover cable. The Windows PC is running Windows 7 SP1 64-bit and the Linux PC is running Slackware 14 64-bit with iptables. My firewall ...
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2answers
192 views

Linux: Blocking outside attempts at attacking computer

in the past when I wanted to block outsiders from attempting to start connections with my Linux machine's various TCP services, what I was told to do was to add this line to /etc/hosts.deny: ALL:...
4
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2answers
8k views

Benefits of REJECT over DROP on a single PC

Recently I learned about the difference between DROP and REJECT in a firewall. I understand that REJECT is better because it closes the connection immediately instead of waiting for timeout as DROP ...
2
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2answers
544 views

Hide logging server from DMZ

I have a server on my DMZ whichs relays syslog and OcsInventory messages to a server on a vlan for logging servers. In order to allow the packets to go through I must allow port 80 (OcsInventory) and ...
1
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1answer
380 views

fail2ban and iptables

Should fail2ban be the master of iptables rules? For example, should I setup my firewall rules along side the fail2ban rules, or should I have all my services configured and managed by fail2ban? ...
1
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1answer
1k views

How could `iptables -F` lock me out of the server? [closed]

I was just configuring IPtables and whilst doing so, had the default chain policies set to ACCEPT, but when happy with the generated rules I changed that to DROP for all chains. I did not run ...
2
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0answers
229 views

Shorewall stopped policies - routeback

Here goes a very specific question about the insides of Shorewall and Iptables in general. Shorewall supports configuration of "Stopped Policies" using the file routestopped, which defines the ...
2
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2answers
1k views

Mixing stateless and stateful firewall rules

I have been advised that mixing firewall rules that are both stateful and stateless can lead to trouble when it comes to troubleshooting. Is there any truth in this? Take the following two rule sets (...
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2answers
460 views

IPTable Security between two servers

Is using IPTables to only allow traffic between two servers considered an acceptable practice? For example TCP traffic on a defined port. I realize this is referred to as an ACL but how secure is ...
3
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1answer
517 views

What are the requirements to sniff UDP packets in a Wireless Ad-Hoc network?

In a wireless Ad-Hoc network, I have two computers which communicates in UDP together from 192.168.1.3 to 192.168.1.5 I have a third computer (192.168.1.6) which wants to listen to the packets which ...
4
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2answers
1k views

Executing arbitrary commands through iptables-restore input

During a pentest I found a way to add arbitrary iptables firewall rules to a server. These rules get applied by way of the iptables-restore command, and I've been wondering whether there is any way to ...
0
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1answer
879 views

Securing my firewall (both dedicated and iptables-based) [closed]

I have an ASA-5510, but I also intend to maintain strict IP tables on my server (Ubuntu 12.04.2), so that there are two layers of "protection". My iptables look like this: *filter # Allows all ...
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3answers
2k views

How can i reject connection from LAN and WAN to some ports?

Scanning with nmap, I discovered that there are 3 open ports on my server. I want to deny any access to these ports from any machine, regardless of whether it is on the same LAN or via WAN. How do I ...
3
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2answers
6k views

How to configure iptables for must open ports?

On my machine there are web services which can be accessed from any PC connected to the same network segment (WiFi for example). I want to use IPtables on the machine to prevent any web services from ...
1
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1answer
5k views

icmp packets not able to reach the firewall despite of adding a specific rule, why?

I am using iptables to allow the icmp traffic in/out of my host. Please find below are the entries from my firewall (linux based):- [root@localhost ~]# iptables -L Chain INPUT (policy DROP) target ...
2
votes
2answers
6k views

IPTables default security rules for a gateway/router?

On a router such as dd-wrt or tomato, what would be some default iptables rules? I am asking for rules on a router/gateway - For example; blocking SYN flood attacks, or XMAS attacks. The basic ...
23
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2answers
10k views

Reject IP packets with an ICMP error, or just drop them?

Consider an internet-facing host (the outer firewall). What should be done with undesired traffic: just drop it, or send back an ICMP error such as port unreachable? (In Linux terms: iptables -P DROP ...
3
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2answers
340 views

Can ipopts be used to circumvent a pf or iptables firewall source IP based blocking?

Can one use ipopts, and in particular IP source routing, to circumvent source-based blocking in pf or iptables? For example, with OpenBSD's pf: block in all # default deny block out all pass in on ...
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4answers
2k views
1
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2answers
2k views

How is iptables useful to prevent attacks against a LAN?

I need some advice securing a LAN using iptables. I've found lots of examples on how to secure single host with iptables, including scanning ports, attacking using ICMP-flood and TCP-flood. These ...
2
votes
1answer
261 views

Consequences of using -s and -d arguments in iptables

We are studying iptables for a Computer Systems Security course. We are confused as to what happens when the -s and -d arguments are both used in the same rule, such as: iptables -A OUTPUT -s 10.7.53....
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1answer
259 views

IPtables - Accept Arbitrary Packets

I've achieved a lot on blocking attacks on GameServers but I'm stuck on something. I've blocked major requests of game-server which it aceepts in the form "\xff\xff\xff\xff" which can be followed by ...
0
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3answers
643 views

Some issues with iptables and nmap

When I scan my pc with nmap I see only one open port. I didn't define any rule in iptables so if I'm not mistaken, all connections should be denied by default. However I can use HTTP or SSH, so that ...