How to use Bitmap Checking in Antispam Admin

Question asked by Scott Hendrickson - 12/17/2015 at 12:16 PM

Unanswered

Hi Everyone!

In Antispam Admin for RBLs, there's a checkbox to Enable Bitmap Checking, but there's no good explanation on how to implement it. In SM's help it says only that you can use this feature if the RBL supports it. I understand the concept of bitmapping (actually bitmasking I think): List A returns 2; list B returns 4; list C returns 8; if the subject is on A and C, the return is 10. However that doesn't tell me what to enter into SM's Required Lookup Value(s) box. Am I supposed to enter the sum of the returns of the lists I want to check? I know I could also just enter the individual returns separated by commas. I just thought bitmap checking would be more efficient.

I look forward to hearing your comments.

Thank you!

Scott Hendrickson
SOS4Net, Inc.
Centennial, CO. U.S.A.

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Scott Hendrickson Replied

1/4/2016 at 1:01 PM

Could someone from SmarterMail please respond to this post? I can find nothing in the documentation that explains how to use Bitmap Checking when configuring an RBL or URIBL. I even checked with Bruce Barnes, one of the most knowledgeable SmarterMail admins out there: Even he didn't have any more info than what's in the docs, which says only that you can use Bitmap Checking if the list supports it. It says nothing about what SmarterMail does with it.

Scott Hendrickson SOS4Net, Inc. Centennial, CO. U.S.A.

Bruce Barnes Replied

1/4/2016 at 7:41 PM

Thanks for bringing this up on the forums, Scott!

Regarding Scott's comments . . . I've been researching the bitmap checking capabilities of both the RBLs included in my antispam document as well as those not included, and have found nothing, on any of the RBL database websites, to indicate whether or not they support bitmap checking.

In the e-mail traffic that has taken place between Scott and myself, he brought up the fact that my current document (as of 31 Dec, 2015), included at least one RBL which had bitmap checking enabled and wanted to know what my experience was with how a rough bitmap might be handled.

My response was, and still is: I have no idea. I've seen nothing and have nothing to report on whether or not this is actually checked by any RBL database providers.

So, group(s): anyone else have anything to contribute with regard to RBL bitmap checking?

Bruce Barnes ChicagoNetTech Inc brucecnt@comcast.net Phonr: (773) 491-9019 Phone: (224) 444-0169 E-Mail and DNS Security Specialist Network Security Specialist Customer Service Portal: https://portal.chicagonettech.com Website: https://www.ChicagoNetTech.com Security Blog: http://networkbastion.blogspot.com/ Web and E-Mail Hosting, E-Mail Security and Consulting

Gabriele Maoret - SERSIS Replied

10/30/2021 at 8:24 AM

I was looking for an explanation of what "bitmap checking" in SmarterMail antispam does and how it works, and I came across this post with no answers ...

Now I ask SmarterTools if it is possible to have a guide explaining how to use this function.

Gabriele Maoret - Head of SysAdmins at SERSIS Currently manages 6 SmarterMail installations (1 in the cloud for SERSIS which provides services to a few hundred third-party email domains + 5 on-premise for customers who prefer to have their mail server in-house)

J Lee Replied

5/2/2023 at 1:58 PM

I have been thinking about this setting, and I agree it is strange that nobody knows what it does.

This setting could allow spam forwarding without triggering the outbound or inbound filters. So you get a spamming email, but you think someone else would like to see it, you forward it and add a message. The bitmap would differ from the original bitmap that Barracuda has on file, so the filter would not trigger on the forward.

If this assumption is correct, then this setting would allow recently changed spam to get through, but would not stop users from forwarding and email that had been scored as spam by one of your RBLs.

If someone at Smartermail could confirm or correct me that would be great.

J. Sebastian Lee Service2Client LLC 6333 E Mockingbird Ste 147 Dallas, TX 75214 - 877.251.3273

Brian Davidson Replied

5/3/2023 at 12:01 AM

I also find it odd there is never an explanation of this setting by SmarterTools. Would love a detailed - or even cursory explanation of the setting!

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