[Mimedefang] Image blocking idea

[WBrown at e1b.org]

DFS wrote on 04/20/2006 09:02:24 AM:

> This is a good idea until spammers start mutating their images.

The same can be said for any spam blockling technique:  It's effective 
until they work around it.  Grey listing worked until they started 
honoring 450 responses.  Bayes worked until the started poisoning it. 
Subtracting points for valid SPF was considered a good idea until spammers 
started registering SPF records.

How long would it take for spammers to start generating a new graphic for 
each message? How much would it slow down the sending for them to do so?