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Accepted
CaptSaltyJack
Asked: 2013-05-14 18:17:09 +0800 CST

iptables doesn't seem to be blocking IPs I ban

  • 772

As a test, I started a TorBrowser, got its IP, and banned it via this command on my VPS:

sudo iptables -A INPUT -s <IP address> -j DROP

I'm still able to surf pages hosted by my server from the TorBrowser. I've even double checked the HTTP access.log to make sure the IP is what I banned, and it is. What am I missing?

My iptables file that gets read in upon boot (via iptables-restore)

#  Allow all loopback (lo0) traffic and drop all traffic to 127/8 that doesn't use lo0
-A INPUT -i lo -j ACCEPT
-A INPUT -d 127.0.0.0/8 -j REJECT

# IP bans
-A INPUT -s 42.121.24.80 -j DROP
-A INPUT -s 121.196.43.157 -j DROP
-A INPUT -s 192.30.85.135 -j DROP
-A INPUT -s 94.102.53.175 -j DROP

#  Accept all established inbound connections
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

#  Allow all outbound traffic - you can modify this to only allow certain traffic
-A OUTPUT -j ACCEPT

#  Allow HTTP and HTTPS connections from anywhere (the normal ports for websites and SSL).
-A INPUT -p tcp --dport 80 -j ACCEPT
-A INPUT -p tcp --dport 443 -j ACCEPT
-A INPUT -p tcp --dport 8080 -j ACCEPT

# Mail
-A INPUT -p tcp --dport 993 -j ACCEPT
-A INPUT -p tcp --dport 465 -j ACCEPT
-A INPUT -p tcp --dport 587 -j ACCEPT
-A INPUT -p tcp --dport 25 -j ACCEPT

# Minecraft
-A INPUT -p tcp --dport 25565 -j ACCEPT

#  Allow SSH connections
#
#  The -dport number should be the same port number you set in sshd_config
#
-A INPUT -p tcp -m state --state NEW --dport 22 -j ACCEPT

#  Allow ping
-A INPUT -p icmp -j ACCEPT

#  Log iptables denied calls
-A INPUT -m limit --limit 5/min -j LOG --log-prefix "iptables denied: " --log-level 7

#  Drop all other inbound - default deny unless explicitly allowed policy
-A INPUT -j DROP
-A FORWARD -j DROP

COMMIT

And iptables -L output:

Chain INPUT (policy ACCEPT)
target     prot opt source               destination         
ACCEPT     all  --  anywhere             anywhere            
REJECT     all  --  anywhere             127.0.0.0/8          reject-with icmp-port-unreachable
DROP       all  --  out524-80.mail.aliyun.com  anywhere            
DROP       all  --  ip196.hichina.com    anywhere            
DROP       all  --  192.30.85.135-IP-Static-VISPERAD.COM  anywhere            
DROP       all  --  tor-exit-nl1.privacyfoundation.dk  anywhere            
ACCEPT     all  --  anywhere             anywhere             state RELATED,ESTABLISHED
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:http
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:https
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:http-alt
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:imaps
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:ssmtp
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:submission
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:smtp
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:25565
ACCEPT     tcp  --  anywhere             anywhere             state NEW tcp dpt:ssh
ACCEPT     icmp --  anywhere             anywhere            
LOG        all  --  anywhere             anywhere             limit: avg 5/min burst 5 LOG level debug prefix "iptables denied: "
DROP       all  --  anywhere             anywhere            

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         
DROP       all  --  anywhere             anywhere            

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination         
ACCEPT     all  --  anywhere             anywhere
iptables

2 Answers

  1. Best Answer

    dmourati asked for iptables -L INPUT for a reason, aka your current rules.
    Before testing the torbrowser, you had the posted rules (or similar).
    Now on the middle of it :

    -A INPUT -p tcp --dport 80 -j ACCEPT

    After that you executed 

    iptables -A INPUT -s <IP address> -j DROP

    So your rule ended up AFTER you accepted all port 80 traffic, thus nothing to DROP since was already accepted.
    You should have added the rule with 

    iptables -I INPUT -s <IP address> -j DROP
    • 7

  2. If you want to give priority to the drop command you need to insert (-I) it before the append (-A) command that allows port 80.

    Order matters, try:

    sudo iptables -I INPUT -s <IP address> -j DROP
    • 2