I just figured out another way to use TMDA that I hadn't previously
thought of. I didn't see this in the FAQ, but if this idea is old news
(or if I missed it in the FAQ), my apologies.
I have a number of daily maintanance crontab entries for root. Some of
these things generate occasional output indicating an error. When this
happens, cron will gather up the output and stick it in an email and
send it to the owner of that cron entry. In the case of root, I've got
an alias that points root to my email address so that I can check the
output of this stuff.
In order to allow this to work I had to put an entry in my whitelist
for [EMAIL PROTECTED] This would allow any spammer to send me email
if they used that from address. Although it hasn't actually happened
yet, I've seen spam "to: [EMAIL PROTECTED]", and spam from lotsa other
addresses @hornclan.com. So I thought I'd be proactive, and try to
figure out how to stop someone from spamming me by claiming to be from
"[EMAIL PROTECTED]"
So what I did was take advantage of the fact that cron allows you to
specify the email address used for mailing output. I stuck the following
in my /etc/crontab:
[EMAIL PROTECTED]
This is, of course, a tmda sender address for "[EMAIL PROTECTED]". Now,
all legit root email will get delivered (which *should* only be generated
by cron) and all illegit root email will generate a response from TMDA.
This creates a problem. If I do get a spam from someone who uses
"[EMAIL PROTECTED]" as the sender address, the response that TMDA
generates will get sent back to "[EMAIL PROTECTED]". Which, in this case,
will get sent back to me. I am in my own whitelist, so I end up seeing
the bounce.
I thought of two fixes for this. The first is to make sure I've set:
BOUNCE_ENV_SENDER = "[EMAIL PROTECTED]"
And then in my incoming filter add:
from [EMAIL PROTECTED] drop
The second fix is to recognize why I have myself in my whitelist.
The reason is that I frequently send myself email when I want to remind
myself of something. I can just take "[EMAIL PROTECTED]" out of my
whitelist and set the following in my outgoing filter:
to [EMAIL PROTECTED] [EMAIL PROTECTED]
This would allow me to send email to myself w/out having to be in my
own whitelist.
Can any of you think of other problems that might crop up from having
done this?
Thanks,
- Mark
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