Blocking SMTP connections: Difference between revisions
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==Blocking== | |||
If a VPS user has been found to be spamming other users, you can block them temporarily from accessing SMTP ports by issuing commands similar to the following on the node that their VPS is situated on: | If a VPS user has been found to be spamming other users, you can block them temporarily from accessing SMTP ports by issuing commands similar to the following on the node that their VPS is situated on: | ||
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iptables -t mangle -D POSTROUTING -s <IP ADDRESS> -p tcp --source-port 25 -j DROP | iptables -t mangle -D POSTROUTING -s <IP ADDRESS> -p tcp --source-port 25 -j DROP | ||
iptables -t mangle -D POSTROUTING -s <IP ADDRESS> -p tcp --destination-port 25 -j DROP | iptables -t mangle -D POSTROUTING -s <IP ADDRESS> -p tcp --destination-port 25 -j DROP | ||
==Rate Limiting== | |||
If you want to reduce their SMTP limits to around 1Mbit per second (66 packets at ~1500 bytes per packet), use the following commands: | |||
iptables -t mangle -A POSTROUTING -s <IP ADDRESS> -p tcp -m multiport --dports 25,465 -m limit --limit 66/sec -j ACCEPT | |||
iptables -t mangle -A POSTROUTING -s <IP ADDRESS> -p tcp -m multiport --dports 25,465 -j DROP | |||
To unblock, just use the -D rules: | |||
iptables -t mangle -D POSTROUTING -s <IP ADDRESS> -p tcp -m multiport --dports 25,465 -m limit --limit 66/sec -j ACCEPT | |||
iptables -t mangle -D POSTROUTING -s <IP ADDRESS> -p tcp -m multiport --dports 25,465 -j DROP | |||
Latest revision as of 13:44, 23 March 2017
Blocking
If a VPS user has been found to be spamming other users, you can block them temporarily from accessing SMTP ports by issuing commands similar to the following on the node that their VPS is situated on:
iptables -t mangle -I POSTROUTING -s <IP ADDRESS> -p tcp --source-port 25 -j DROP iptables -t mangle -I POSTROUTING -s <IP ADDRESS> -p tcp --destination-port 25 -j DROP
To unblock, just use the -D rules:
iptables -t mangle -D POSTROUTING -s <IP ADDRESS> -p tcp --source-port 25 -j DROP iptables -t mangle -D POSTROUTING -s <IP ADDRESS> -p tcp --destination-port 25 -j DROP
Rate Limiting
If you want to reduce their SMTP limits to around 1Mbit per second (66 packets at ~1500 bytes per packet), use the following commands:
iptables -t mangle -A POSTROUTING -s <IP ADDRESS> -p tcp -m multiport --dports 25,465 -m limit --limit 66/sec -j ACCEPT iptables -t mangle -A POSTROUTING -s <IP ADDRESS> -p tcp -m multiport --dports 25,465 -j DROP
To unblock, just use the -D rules:
iptables -t mangle -D POSTROUTING -s <IP ADDRESS> -p tcp -m multiport --dports 25,465 -m limit --limit 66/sec -j ACCEPT iptables -t mangle -D POSTROUTING -s <IP ADDRESS> -p tcp -m multiport --dports 25,465 -j DROP