Backscatter
From ITS Wiki - Information Technology Services - University of Rhode Island
| Networking This page is part of a category. To see more pages like this, go to the Networking index. |
| Email This page is part of a category. To see more pages like this, go to the Email index. |
Contents |
What is Backscatter?
"2,000,000 spams, 40% bounce rate, 9% of mail servers send backscatter... That means that for that two million spam run, 72,000 bounce notifications (NDRs) are going to be sent back to the sender address. Since spammers forge the sender's address, this mail is going to be be received by people who had nothing to do with the spam. This, in a nutshell, is backscatter. And there's a lot of it floating around." - Spam Resource
Types of Backscatter
- Misdirected bounces from spam runs, from mail servers who "accept then bounce" instead of rejecting mail during the SMTP transaction.
- Misdirected "please confirm your subscription" requests from mailing lists that allow email-based signup requests.
- Challenge requests from "Challenge/Response" anti-spam software.
- Misdirected virus/worm email notifications from virus scanners.
- Out of office or vacation autoreplies and autoresponders.
Stopping Backscatter
1. Do not set an "out of office" reply. This sends random notes out to the world telling whoever receives the notice that you have a live email address.
2. Do not use a "Challenge/Response" anti-spam application or service. Your challenge requests are just another kind of backscatter.
3. Report backscatter as spam via your spam-reporting service. It helps to collect statistics on the problem.
If You Administer a Mail Server
- Don't use Challenge/Response, and don't allow your users to, either. Few, if any implementations of C/R are smart enough to prevent responses to spam messages.
- Don't run autoresponders, out-of-office notifications, etc. Your mail could end up being blocked.
- Don't bounce mail after accepting it from a remote site.
- Only allow web-based signups for your email lists.
Related Links:
http://www.spamresource.com/2007/02/backscatter-what-is-it-how-do-i-stop-it.html
