CDR: Re: Anonymous Remailers

[Ryan McBride]

On Wed, 4 Oct 2000, dmolnar wrote:
> if an adversary knows you are running a middleman and has control over
> one of the hosts relaying mail for your ISP, it may be able to
> 
> 	1. send mail ostensibly to a legitimate, remailer address
> 	via your "middleman" remailer
> 
> 	2. intercept the message you send out at the captured mail
> 	relay
> 
> 	3. change the header so the mail you thought was going to
> 	a remailer ends up in someone else's e-mail account. or
> 	maybe the e-mail account of the adversary so he can
> 	pose as an aggreived user.  
>
> A contact to the ISP follows. You can try to convince your ISP that
> "no, this shouldn't happen because I'm running as a middleman," 
> but it's not clear how you could prove that you're under this kind of
> attack.

An individual can simply fabricate an e-mail outright (requesting the help
file to provide himself with an easily-modified template and log entries
on on the mail relayy) or just not even show it. "Umm...Like I got this
death threat... but I deleted it" would be sufficient for some of the more
spineless providers.

> I'd have to go read the code to figure out whether a plaintext message
> could be sent this way, or just a message actually encrypted to another
> remailer. 

It seems as though if you're running as a middleman and you encounter a
plaintext message, it'll encrypt the message with the next remailer's key
before it mails it out. But I only took a quick look at the code.

-Ryan

--
Ryan McBride - mcbride at countersiege.com
Systems Security Consultant
Countersiege Systems Corporation - http://www.countersiege.com