YOU ARE ISP AND YOUR NET RANGE GOT BLACKLISTED ?
We really feel sorry for you because this should not happen to respectable professional ISPs, and we do our best to prevent this.
Here are 4 things that we recommend in order to stay off the UCEPROTECT-Blacklists and the Backscatterer List:
1. Do not use abusive techniques on your systems, and also tell your customers with their own servers not to do so.
The following techniques are considered abusive, even though some seem to have become very popular.
Sender callouts (also known as Sender Verify or SAV) or any other kind of Backscatter.
Simply use common sense before turning on any new technique. If a technique or procedure makes your system capable of being a part of a DDOS against others, then you should not use it.
2. Ensure that large amounts of garbage cannot be sent through your smarthosts.
Spammers always try to send millions of emails for it to be worthwhile, it is a numbers game for them. On the other hand, you will not find many end users having a genuine need to send more than a few hundred, or at most a few thousand, emails per day per account.
Therefore it is advisable to establish appropriate transmission limits on all smarthosts. Users who have demonstrated that they do not abuse your infrastructure, and who claim to have a higher need, can easily be given higher limits or even no limits. It is also very unlikely that regular users will send email to more than 10 undeliverable recipients per hour.
Users sending email to multiple undeliverable addresses within a short time frame are almost always spammers, therefore you should shutdown those accounts automatically and promptly.
Furthermore it should be no problem to filter all outgoing emails for viruses etc on each smarthost.
3. Ensure that your dynamic / dialups cannot be abused as spam zombies.
Block all outgoing connections from client dynamic / dialups to Port 25 and force them to connect to your smarthosts instead [Port 587 is in common use].
Then, if a user's computer becomes infected by malware, propagation will be impossible or at least contained very quickly.
This way, any damage stays within limits and it will be unlikely that blacklists become aware of your system.
4. Prevent open relays and open proxies at your dedicated line customers and at customers with static IP addresses.
Examine the IP addresses of customers with ‘statics’ regularly (e.g. weekly) with automated scripts for such weaknesses. Temporarily shut down those IP addresses that you find to have exploitable security holes that can lead to email abuse.
You will immediately have less work in your abuse department and less problems with blacklists.
On a long-term basis this will also maximize your profits...
We all know that you do not earn money with a flat-rate customer if his/her computer is busy 24/7 dispatching spam, viruses and worms to the world...
If you are actively preventing his/her computer from sending the crap, it is very unlikely that this customer will be able to send the traffic in other ways :-)
Note that, if every service provider worked in this way, there couldn’t be a spam nor a virus problem on this planet.
If you need technical assistance on making your network unattractive for spammers, or if you still search for a really efficient spam protective system for your infrastructure, do not hesitate to contact us.
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