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Server

No internet access after config iptables

user406126

10/28/22, 12:46 PM

After that configuration:

iptables -P INPUT DROP
iprables -A INPUT -j DROP
iptables -P OUTPUT ACCEPT
iptables -A OUTPUT -j ACCEPT

Now can't access internet normally or through VPN. What's wrong?

563

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iptables

connection

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Server

vidarlo

10/28/22, 12:54 PM

Now can't access internet normally or through VPN. What's wrong?

You told your computer to drop any and all incoming packages. It's doing that. Nothing is wrong, but you told your computer do something which obviously is not what you want.

After setting the default target to DROP, you'll have to add allow rules to allow certain kinds of traffic. This may for instance be established connections:

iptables -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT

Which will roughly speaking allow answers to outgoing connections. As you don't state what you want to achieve, any more accurate answers is impossible. But a suggestion would be to look into e.g. ufw, as it hides some of the complex magic from you.

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user406126

10/28/22, 12:58 PM

thx for answer, my intention is normal user => none can access the machine but I can navigate through the web

vidarlo

10/28/22, 1:03 PM

If you don't have a fair understanding of how TCP/IP works, you should stay with tools such as `ufw` that hides the details from you. Raw iptables rules requires knowledge of how the protocols works.

user406126

10/28/22, 1:08 PM

I got basic notions. Im under cyberbullying since 4 years. Discovered yesterday that my ufw were allowing all traffic. Supposed that have been hacked so moved to iptables to do it manually. If can give any advice or resource it would be great.

vidarlo

10/28/22, 1:10 PM

UFW is a frontend for iptables. It only helps you configure sane settings in a friendly manner; it relies on iptables for actually handling the traffic.

user406126

10/28/22, 1:20 PM

thank you. I thought that if set OUTPUT to ACCEPT it allow me. Now with the command you shared can, hope that my machine will be protected now.

vidarlo

10/28/22, 1:23 PM

Based on your other threads on Unix SE: Consider educating yourself on the operating system you're using; I'm tempted to believe that the *hacking* you're claiming is the result of your own actions, and not any malicious third party.

user406126

10/28/22, 2:52 PM

Have did a bit of research; Can tell me what difference between <conntrack> & <state>, && <--ctstate> & <--state>? Thank you.

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: No internet access after config iptables

TH: ไม่มีการเข้าถึงอินเทอร์เน็ตหลังจาก config iptables

RO: Nu există acces la internet după configurarea iptables

RU: Нет доступа в интернет после настройки iptables

VI: Không có truy cập internet sau khi cấu hình iptables

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