a technological barrier designed to prevent unauthorized or unwanted communications between computer networks or hosts

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iptables and hacker prevention

Hello fellow Ubuntuers! here is an example of my iptables.rules file: *filter :INPUT ACCEPT [0:0] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [0:0] :f2b-sshd - [0:0] :f2b-sshd-ddos - [0:0] -A INPUT -p tcp ...
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91 views

Why does remote SSH connection time out?

My server runs Ubuntu Server 14.04. When connecting over SSH from a local LAN client it works fine. When I connect using a different machine from an outside network, I get 'connection timed out'. I ...
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73 views

Is port 5432 open for postgres?

Here is the output of the netstat command on ubuntu 14.04 server: admin@ibm-testbox:~$ netstat -tulnp | grep 5432 (No info could be read for "-p": geteuid()=1000 but you should be root.) tcp 0 ...
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34 views

Server iptables configuration

I have an application installed in the /usr/local/tomcat/fakebook directory. I want to allow any user to use the app and also all external user to use the app. I just want to allow connections to the ...
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52 views

UFW not opening port

Could someone explain why I can't open port 64738? I opened it with sudo ufw allow 64738 But when I test with nmap, the port is still closed. > sudo ufw status Status: active To ...
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35 views

Can't connect to external IP

My local IP is 192.168.1.2 I have multiple servers running including a web server. If I point my pc's browser to localhost:80, 127.0.0.1:80 or 192.168.1.2:80 it loads. If I point my android's ...
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1answer
65 views

Allow only a specific ip address to an open port

I have a Zimbra server and the admin port, 7071, is open to the world. I had someone try to get into it yesterday and that locked the account. I was wondering if I can block all access to this port ...
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17 views

Comodo and GUFW

Good morning to all. My question has to do with the use of GUFW for blocking traffic except the updates for Comodo for linux AV. I need a safe pc that will be used only for checking and cleaning usb ...
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29 views

How do you whitelist an IP address with just one line command?

I've been searching how to whitelist a IP address (ex. 123.123.321.1) with Ubuntu 12.04. But everyone seems to give long elaborate answers. Is there just 1 simple command to whitelist an IP address? I ...
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43 views

Still seeing connections from IP after blocking in fw

So I'm using iftop to monitor connections on my server, and I'm seeing this ip address 116.110.127.24 making constant connections on ssh port. (I'm not sure if this means 22 or my actual ssh port, it ...
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1answer
40 views

how can i kill all established connections before running iptables bash scrip

there is established connection from before running iptables bash script, and even this connection is blocked by iptables, but it keeps running because it is in established status, which according to ...
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344 views

ssh connection refused

Hi I'm having a problem with my ssh, which is magically stopped working and I couldn't figure out why. The message it give is: ssh: connect to host <host> port 22: Connection refused I don't ...
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74 views

UFW block 80 port? 14.04

Im using ubuntu 14.04.On ufw 80 , 80/tcp , 80/udp is allowed from all. But when i look to logs. its look like this *my server ip YYY.YYY.YYY.YYY *and i delete my mac and ip Feb 21 16:59:14 server ...
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1answer
71 views

How can I dynamically determine the IP mask to use for dynamic ranges?

I have a list of ranges for IP addresses that I want to block, the ranges are like 210.80.32.0 to 210.80.63.255 How can I dynamically determine the right 210.80.32.0/NUMBER to capture the full range? ...
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53 views

OpenSwan Configuration

I am trying to set up IPsec tunnel between two hosts. Host A has an IP 10.2.40.3 and Host B has an IP 10.2.60.4 Host A is connected to the router with its GW being: 10.2.40.4 Host B is connected to ...
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56 views

How to allow DHCP between 2 networks using Shorewall?

I have a server with hyper-v and 3 networks: eth0 is virtual, eth1 is physical, eth2 is extranet from ISP. Virtual network has a DHCP running and all virtual machines can reach it fine. But not the ...
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27 views

the packet flow from a network interface to a local process? help!

I'm read Linux Iptables Pocket Reference. So I do not understand the figures presented. It says that packets travel through chains, and are presented to the rules one at a time and in order. Then ...
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71 views

Configure Ubuntu 14.04.3 firewall for NAS TS-453A

With Qfinder I can manage my QNAP TS-453A from my Ubuntu 14.04.3 LTS laptop, only when the firewall in Ubuntu is disabled. As soon as the firewall is active, Qfinder and the NAS stop both and are not ...
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56 views

Recover Server from recovery mode(firewall closes ports)

My server( Ubuntu 14.04 - Plesk - RAID1 ) is now in normal mode. Almost all ports disabled by firewall as plesk port 8443, so plesk login panel is not opening. Also Website is not opening. ...
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1answer
117 views

apt-key add <file>; apt-get … keyserver timeout on same key

I'm behind a firewall (i have the proxy setup - just like in Why does add-apt-repository now fail to retrieve keys behind my proxy server, but I can update package lists and manually receive the ...
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14 views

Output SSH in shorewall

I can not use ssh or scp where has installed shorewall, returns me the message: ssh: connect to host xxx Connection refused Which should add a rule to enable this feature?
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115 views

IPTables forward port to another ip:port but keeping original source ip

I have following iptables rules on gateway machine(192.168.0.1). I want to forward port 192.168.0.1:80 to 192.168.0.2:8080. But I need to maintain original source ip so that original server can get ...
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0answers
37 views

Firewall not starting on system startup

I have enable firewall using sudo ufw enable. But when i restart system, it is getting disabled. I checked /etc/ufw/ufw.conf and it has ENABLED=yes. Here is system config $ uname -a Linux master ...
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51 views

How can i configure a rule that using squid3 for AVG update proxy base on an external firewall?

I'm using Ubuntu Desktop 14.04.3. The firewall i'm using is here http://gufw.org/. I've set up squid3 with a specific port. Now i want to configure the firewall rule to allow only AVG antivirus ...
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36 views

Block HTTPS site

Can anyone recommend an effective tool to block some https websites with ubuntu server? I want to use the server as a gateway for the users. A detailed guide would be highly appreciated. Thanks
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27 views

Block anything from NO-IP source

i have problem in my server there is to much load in my server and all process is 100% and at last server go down the only strange thing i can see there is to much request from no-ip how can i block ...
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36 views

UFW ACCEPT Problem

I'm having problem with UFW. If i block like whole /24 network becouse lots of bruteforcing etc. coming from China / Korea or somewhere. They still get to open ports. If i have, lets say port 443 ...
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1answer
450 views

Unable to connect to mongo on remote server

I have installed mongo on machine1(Ubuntu 14.04.3 LTS server) in my local network. I have also opened the port 27017 as mentioned in this guide using following commands: sudo iptables -A INPUT -p tcp ...
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1answer
59 views

Unable to add firewall rule “Duplicate Profile”

I'm unable to add new rules to my firewall using ufw gui. In the Log I get the following error. [19/01/16 14:16:43] Error running: /usr/sbin/ufw allow in from any to any port 8000 > WARN: ...
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96 views

OpenVPN Configuration with ufw eth0 doesn't exist to add it in before.rules

in this guide I am asked to edit /etc/ufw/before.rules and add: # START OPENVPN RULES # NAT table rules *nat :POSTROUTING ACCEPT [0:0] # Allow traffic from OpenVPN client to eth0 -A POSTROUTING -s ...
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60 views

ufw is enable but still be able to surfing web

I enabled ufw as a security practice. And let the default setting intact. I noticed that I still be able to access internet using web browser, so I tested the firewall with transmission. Transmission ...
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69 views

How does ufw filter traffic?

I enabled ufw firewall with the following command: $ sudo ufw enable Firewall is active and enabled on system startup $ Now while I look at the status: $ sudo ufw status verbose Status: active ...
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1answer
49 views

Would active connections cause this UFW Block?

I'm running ubuntu 14.04 as a gateway, routing is controlled by iptables. I'm getting a number of strange blocks in UFW which seem to effect established connections. Is there any way this block would ...
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109 views

Server setup problems, am I missing something obvious?

So I've set up Ubuntu 14.04 as a LAMP. I've got it set up to do three things so far, all work fine over LAN. 1) Network printing. 2) Host a small webpage. 3) Act as a minecraft server. I've ran a ...
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1answer
65 views

Do I need iptables if only two ports are open to the public?

For a special task I have a root server running Linux Ubuntu 14.04. The server has a very minimalistic installation with ssh on a non-standard port and no root access. Basically the servers primary ...
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37 views

Unable to recieve UDP packets

I have a program which sends UDP packets to a specific port (eg: 53023) at localhost. I have written another program using Qt 4.8 which tries to receive the packets from this port at localhost. ...
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1answer
45 views

Telnet and Firewall [closed]

I would like to transfer file from one machine to another using telnet. When I tried to connect the two computers by telnet, using the same network, the file was sent correctly and everything was ...
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112 views

UFW is not logging (port scan with nmap)

This is the output of sudo ufw status verbose: Status: active Logging: on (low) Default: deny (incoming), deny (outgoing) New profiles: skip To Action From -- ...
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Do I need iptables or ufw if I have gufw?

On my Ubuntu computer I have Iptables,ufw and gufw installed on it but I am trying to figure out if I need to remove one so I did a experiment and removed iptables and I saw ufw and gufw was removed ...
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45 views

Why does Ubuntu comes with two firewalls by default?

I just realised Ubuntu comes with two firewalls by default iptables and ufw. But why? I mean running more than one software firewall on one computer can be insecure, that's what they say. I don't ...
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213 views

Wildfly on Ubuntu HTTPS on port 8443 timeout

I have a web application (Java EE) which was running on a Windows server without any problem. Also on my local machine (Mac OS) everything runs smoothly. Now I had to replace the remote Windows server ...
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2answers
173 views

cannot telnet into ubuntu from windows 7

I have a php server running on port 4444 on my Ubuntu 15.04 machine. Now when I execute telnet 127.0.0.1 4444 it works fine. Now I have connected my machine and a windows 7 machine using mobile ...
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128 views

UFW is blocking “gvfsd-smb-browse” on changing ports

I have a problem connecting to the samba shares between two of my computers. One is a Laptop and the other a Destop-PC, both running Ubuntu-Gnome 15.10. It changes from which Computer I can connect to ...
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41 views

Allowing sshd on local network without access to internet

I have setup sshd on my server and can access it fine from both my local network and remotely from other networks. I set up port forwarding using a different port than port 22. Port forwarding is ...
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1answer
58 views

VSFTPD not letting me login

Any one come across this before, Other then the settings below everything is default. This seems to work on my local machine but not on a VPS local_enable=YES write_enable=YES anonymous_enable=NO ...
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104 views

Vagrant NFS folders + Firewall rules

I am trying to configure the firewall -via the GUI tool- on 14.04 by adding rules to allow NFS folder sharing with my vagrant box. However this only works when the firewall is disabled as on vagrant ...
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758 views

How to configure UFW to allow ntp to work?

I've enabled UFW on one of production servers with configuration: Default: deny (incoming), deny (outgoing). For NTP synchronization, I've installed ntp and it's currently running. Can someone advise ...
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31 views

xrdb to Ubuntu machine not working from external network

I have a Ubuntu machine that I would like external users to connect to using RDP. Connecting from an internal network works perfectly fine. But users outside of my network,who use the public IP, can ...
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19 views

How to notify administrator with mail in case ubuntu firewall stops

Is there a notification application to warn administrator in case Ubuntu firewall stop accidentally ? Thank you.
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97 views

configure iptables to redirect traffic to a specific IP address

I have just began using iptables. I have a server with a public ip address (A.A.A.A) wich is hosting a Virtual Machine (B.B.B.B) on local network. I want to redirect all inbound traffic on the port ...