I am trying to find the way to block all web-pages that I browse that use plaintext password for their logins with iptables.
Here is the command I tried, something it wrong with it. How do I enter this command? This is for educational purpose only. Say, if I use "password" for all my logins.
Thanks.
nata#nata-VirtualBox:~$ iptables -A OUTPUT -s match --string "password" --dport 80 -p tcp -j DROP
iptables v1.4.12: unknown option "--string"
Try `iptables -h' or 'iptables --help' for more information.
nata#nata-VirtualBox:~$ iptables -A OUTPUT -m string --string "password" --dport 80 -p tcp -j DROP
string: Could not determine whether revision 1 is supported, assuming it is.
iptables v1.4.12: unknown option "--dport"
Try `iptables -h' or 'iptables --help' for more information.
Try with this:
iptables -A OUTPUT -p tcp --dport 80 -m string --string password --algo bm -j DROP
To get help on a specific match, you can do:
iptables -m Match-Name --help
Related
First, I set up my firewall like this to allow everything:
sudo iptables -P INPUT ACCEPT
sudo iptables -P OUTPUT ACCEPT
sudo iptables -P FORWARD ACCEPT
sudo iptables --flush
Then, I check if NTP is working:
sudo systemctl daemon-reload
sudo systemctl restart systemd-timesyncd
timedatectl
and I can see that it says System clock synchronized: yes.
But then if I reboot and set up my firewall like this (reject everything except for NTP):
sudo iptables -P INPUT REJECT
sudo iptables -P OUTPUT REJECT
sudo iptables -P FORWARD REJECT
sudo iptables -A INPUT -p udp --dport 123 -j ACCEPT
sudo iptables -A OUTPUT -p udp --sport 123 -j ACCEPT
then I get System clock synchronized: no and the clock won't sync.
Based on the above steps, I'm convinced it's the firewall that's blocking timesyncd. I have read (for example, here) that perhaps it has to do with extra ports being opened by the service or the fact that is uses SNTP instead of NTP. I have tried different combinations of rules, but with no success yet as I am not an expert with iptables.
But there must be a way to set it up such that it works without altogether disabling the firewall.
Summary
--dport and --sport are switched.
Explanation
For the other services that I am allowing through the firewall, my machine is the server. For NTP, my machine is the client. Because the rest of my original configuration actually looked more like this:
...
sudo iptables -A INPUT -p tcp --dport 443 -j ACCEPT
sudo iptables -A INPUT -p tcp --dport 80 -j ACCEPT
sudo iptables -A INPUT -p udp --dport 5353 -j ACCEPT
...
sudo iptables -A OUTPUT -p tcp --sport 443 -j ACCEPT
sudo iptables -A OUTPUT -p tcp --sport 80 -j ACCEPT
sudo iptables -A OUTPUT -p udp --sport 5353 -j ACCEPT
...
I assumed that --dport was meant to be used with INPUT and --sport was used with OUTPUT. However, you have to think about what it means. To use NTP as a client, I need to allow INPUT packets that are coming from a source port of 123, not input packets that are coming to a destination port of 123. Likewise, I need to allow OUTPUT packets with destination port 123, not output with source 123.
So the answer to my question is to use this:
sudo iptables -P INPUT REJECT
sudo iptables -P OUTPUT REJECT
sudo iptables -P FORWARD REJECT
sudo iptables -A INPUT -p udp --sport 123 -j ACCEPT
sudo iptables -A OUTPUT -p udp --dport 123 -j ACCEPT
here is my whitelist allowing wikipedia and rejecting all other sites. Unfortunately this script does not work : I cannot connect to wikipedia. Why ?
Thank you
Allow incoming traffic from established connections.
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
Allow incoming connections from wikipedia
iptables -A INPUT -s 78.109.84.114 -j ACCEPT
Allow outcoming connections from wikipedia
iptables -A OUTPUT -s 78.109.84.114 -j ACCEPT
Drop other incoming connections.
iptables -P INPUT DROP
Drop any transfer of traffic.
iptables -P FORWARD DROP
I think i got your Problem.
Try using iptables -A OUTPUT -d 78.109.84.114 -j ACCEPT instead of
iptables -A OUTPUT -s 78.109.84.114 -j ACCEPT
And if you want to work with the state module then use:
iptables -A OUTPUT -m state --state NEW -d 78.109.84.114 -j ACCEPT
The Problem is, that you create a rule, that says that Traffic that goes into the OUTPUT Chain with the Source Adress 78.109.84.114 is allowed. But what you want is a rule that allows Traffic to Wikipedia outgoing not from Wikipedia.
The following will drop packets which contain the string specified:
iptables -I FORWARD -j DROP -p tcp -s 0.0.0.0/0 -m string --string "therichsheickc#yahoo.com"
The string is one which a botnet spammer uses (from 1000's upon 1000's of ip addresses) to hammer my email servers constantly. This rule is somewhat effective, but doesn't stop the connections. I'd like it to -j DROP the IP as well after a match. Can I do this in iptables without going to userspace?
This particular scanner always greet with EHLO 192.168.2.33. Use these rules to stop them:
iptables -t raw -A PREROUTING -i eth+ -p tcp --dport 25 -m string --string "192.168.2.33" --algo bm -m recent --set --name SBOT
iptables -I INPUT -i eth+ -p tcp --dport 25 -m recent --rcheck --name SBOT -j REJECT --reject-with tcp-reset
or maybe this will help :
iptables -A FORWARD -m string --algo bm --string "therichsheickc#yahoo.com" -j DROP
I can't access Plesk Amdin because of DOS attack; can I block a hostname or IP address through SSH? If so, how would I be able to do this?
Thank you!
If you have iptables you can block it using simple rule:
iptables -I INPUT --source 1.2.3.4 -j DROP
This rule drops packets coming from IP 1.2.3.4.
Probably the easiest is to SSH to your box use vim to and add the following to the top of your .htaccess file in the root of your domain (/var/www/vhosts/yourdomain.com/httpdocs/.htaccess):
deny from 12.345.67.89
Obviously replace the IP address with the one you want to block. Repeat this for any sites you think are being attacked.
iptables -I INPUT -p tcp -s 1.2.3.4 -m statistic --probability 0.5 -j DROP
iptables -I INPUT n -p tcp -s 1.2.3.4 -m rpfilter --loose -j ACCEPT # n would be an numeric index into the INPUT CHAIN -- default is append to INPUT chain
iptables -I INPUT -p tcp -m hashlimit --hashlimit-mode srcip -s 1.2.3.4 --hashlimit-srcmask --hashlimit-above 9/second -j DROP
iptables -I INPUT -p tcp -s 1.2.3.4 -m limit --sport 80 --limit 100/second -j ACCEPT
There are countless others for your circumstances.
Sincerely,
ArrowInTree
how do I drop all traffic to smtp, except originating from my IP? This example I found drops traffic for particular IP, I need to deny by default, but allow 1 IP in. Thanks
# iptables -A INPUT -s 65.55.44.100 -p tcp --destination-port 25 -j DROP
iptables -A INPUT -s ! 65.55.44.100 -p tcp --destination-port 25 -j DROP
# iptables -A INPUT -s 65.55.44.100 -p tcp --destination-port 25 -j ACCEPT
# iptables -A INPUT -p tcp --destination-port 25 -j DROP
If you actually want to deny all traffic by default, and only open up holes for specific protocols/addresses/etc., what you want to do is continue to use the rule you have now, and also modify the default policy like so:
# iptables -P INPUT DROP
Otherwise, siposa's answer will drop all SMTP traffic except for the specified IP address, while not affecting other protocols.