> For the complete documentation index, see [llms.txt](https://www.pwny.cc/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://www.pwny.cc/so/linux/iptables.md).

# Iptables

### Delete current rules and chains

```bash
iptables --flush
iptables --delete-chain
```

### Allow loopback

```bash
iptables -A INPUT -i lo -j ACCEPT
iptables -A OUTPUT -o lo -j ACCEPT
```

### Drop ICMP

```bash
iptables -A INPUT -p icmp -m icmp --icmp-type any -j DROP
iptables -A OUTPUT -p icmp -j DROP
```

### Allow SSH, HTTP, DNS

```bash
#SSH
iptables -A INPUT -s 10.10.10.10/24 -p tcp -m tcp --dport 22 -j ACCEPT

#HTTP/HTTPs
iptables -A INPUT -p tcp -m state --state NEW -m tcp --dport 80 -j ACCEPT
iptables -A INPUT -p tcp -m state --state NEW -m tcp --dport 443 -j ACCEPT

#DNS
iptables -A INPUT -p udp -m udp --sport 53 -j ACCEPT
iptables -A INPUT -p tcp -m tcp --sport 53 -j ACCEPT
iptables -A OUTPUT -p udp -m udp --dport 53 -j ACCEPT
iptables -A OUTPUT -p tcp -m tcp --dport 53 -j ACCEPT
```