[Mimedefang] regex filter unwanted words

[John Rudd]

dick hoogendijk wrote:
> Some time ago I asked about filtering unwanted words. The advice was /
> is not to do it, but I still want to try.
> 
> The filter rule was something like:
> 
> if($Subject =~ m// ) {
>  	return action_bounce("bad subject");
> }
> 
> Question: do I put the unwanted words into this rule like this:
> 
> if($Subject =~ m/sex|microsoft|Watch/ ) {
>  	return action_bounce("bad subject");
> }
> 
> I'm not sure how to put in the regex. How many words can I put between
> those two slashes of m// ?
> 

As many as you can fit.  But I would be very careful about it.  Plus, I 
would make sure to use "\b" around the words, so that you're not getting 
sub-string matches.  For example:

\bsex\b  will match "sex" but not match "Wesex".

So, maybe something like this:

if($Subject =~ m/\b(sex|microsoft|Watch)\b/ ) {
	return action_bounce("bad subject");
}

However, as others have pointed out, it's not generally a good idea. 
Spammers change their subjects often enough that you'll have trouble 
keeping up.  Plus, you'll be very prone to false-positives.