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six demon bag

Wind, fire, all that kind of thing!

2010-06-14

Active Directory Documentation

When you inherit an existing (usually home-grown) Active Directory, it can be a real pain to figure out how the thing was actually configured by the previous admin(s). In a situation like that it's kinda nice to have a tool at hand that'll do the dirty work for you.

Of course there's pay-ware like ADscribe, but personally I find $99 kinda expensive for something you're going to use every other decade (or so). Microsoft's own Active Directory Topology Diagrammer is freeware (well, sort of, since it requires Visio), but it has to be installed, and the results weren't that convincing when I tried to run it from outside the target domain.

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Posted 21:37 [permalink]

2010-05-30

Backscatter protection

What is backscatter?

When mail servers accept mail and later discover that for some reason they are unable to actually deliver it, RFC 821 specifies that a Non-Delivery Notification (NDN, also known as "bounce") must be sent to the originator of the mail.

However, the "From" address can be spoofed most easily, so there is no guarantee whatsoever that the mail actually originated from that address. In case of a spoofed address, the NDN will be sent to someone who hadn't sent the original mail to begin with. These bounces going back to someone else but the original sender are called "backscatter".

Why is that a problem?

Because spammers tend to send their bulk e-mails to anything that looks even remotely like an e-mail address, the "To" addresses usually include lots of invalid addresses. Therefore spam-runs can cause massive waves of backscatter flooding the mailboxes of those people whose addresses were spoofed in the "From" field. However, it's not sensible to simply block all incoming bounces, because there are legitimate bounces as well.

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Posted 22:41 [permalink]