gnupg encrypted mail and malware/spam

Thomas Scheffczyk
Sat May 10 20:14:02 2003

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Hello all,

I don't know if this topic was discussed before, my searches in the list 
archive were not successfull, but perhaps I used just the wrong keywords.

Here is my problem:

If gnupg is used to protect mail messages it also disables all server 
based protection measures against malware and spam. No virus scanner nor 
spam filter an firewalls or gateways can check the encrypted messages.

All protection is to be done on the host where the mail is decrypted. At 
least for bigger networks this is nearly impossible do do: No system 
administrator will be happy if most of the defence lines will be 
unusable and without doubt is needs a lot more manpower to secure all 
local workstations to a level comparable with a firewall.

I guess that this problem is very sensitive, especially in the gnupg 
community; because standard solutions would be key escrowing or 
automativally co-encryption with corporate keys.

Gnupg is used for various task within the network I'm responsible for 
and I really want to give all users access to gnupg to allow them to 
protect their privacy and the data that is transferred by mail, but I 
can't risc the security and integrity of the network itself.

Any solutions, hints, positive and even negative experience with this or 
simillar problems is very desired.



PS: I do not fear 'ordinary' viruses or other malware. What i really 
fear is a sophisticated attacker that send on a very slow rate backdoors 
to single users in my network. I can not guarantee the really no user 
will start the program. If it is started, it's easy to create a 
backchannel over allowed traffic like http.

PPS: I hope the I don't awake sleeping dogs, but what would happen, if 
spammers would start to send encrypted messages? All countermeasures 
like spamassassin or even statistical token analysis wouldn'd stop this 
kind of spam.

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