How can I stop attempts to harvest addresses from my server?

Question

I have heard of a program that searches mail servers for email addresses. All you do is put one valid email address in the server and it searches the entire email server and returns valid email addresses. Then a spammer can take these valid addresses and spam your company and users! How can I block programs like this from working.

Answer

Many of these programs designed to gather addresses work by opening multiple connections to your server (up to 512 threads in some cases) and will automatically reconnect if disconnected.

They then try and guess every combination of username on your server using a brute force method.

If you know the address the attack is coming from you can use the Banned Hosts option within GMS Anti-Spam to ban the IP the program is being run on from your server altogether.

However, even if you do not know where these attacks are likely to come from you can utilise the GMS Anti-Spam > AI > Machine name checks to monitor activity on the IP addresses connecting to your server.

If the AI feature sees a number of axcessive connections from any one IP address to your server, it can automatically stop any further connections from that IP.

See Also:

• Can I slow SMTP responses to bad commands?

Keywords:Address, harvest, spam, search