[Gross] Spammers adapt

Eino Tuominen eino at utu.fi
Thu Feb 28 23:17:35 EET 2008

Jesse Thompson wrote:
> sjsms_response_grey = $X4.4.3|$N$D1000|Please$ try$ again$ later
> sjsms_response_match = $D$Y1000
> We haven't tried this technique in production.

I had some problems with that before. Though I think it was to do with 
mailing list expansion done at the reception time. I had to configure 
iMS to expand all mailing lists at the backend because of it. I have to 
check old conversations on iMS list about it...

> we raised filter_bits to 25 a while ago after experiencing significant 
> false positives in the bloom filters.  Now, we're starting to see that 
> again, so we might need to raise it again.

I remembered that, and I decided to go straight up to 26 as it's still 
only a 100 megabytes of memory.

> One additional note, the bloom filter false positives tend to occur when 
> there is a lot of repetition in the from/to values.  You should 
> doublecheck that your match percentage is not actually due to these 
> false positives.

I'll run a more thorough analysis tomorrow.

> That would be awesome.
> I think we discussed similar ideas here:
> http://code.google.com/p/gross/issues/detail?id=42

Yup, that's just the same block_threshold I'm talking about.

> Don't forget to allow for a weight to be assigned to sophos blocker 
> matches.

I'll get back to this tomorrow.

   Eino Tuominen

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