Image filter: Trigger on any external linked content?

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Image filter: Trigger on any external linked content?

Beitragvon VanguardLH » 9. Feb 2008, 04:45

I am wondering how the Image filter operates that is included in the install of Spami. Does it trigger (i.e., block e-mails) based on:

#1 - An <IMG> tag?

#2 - An <IMG> tag with a src=<url> parameter?

#3 - An <IMG> tag with a src=<url> parameter which has in the URL the "?" or "@" characters used to delimit parameters within the URL and used to pass ID strings to the file server?

#1 would not be appropriate. #2 might be how the Image filter works but then even a company logo in the purchase order they send to you would get that email tagged as spam. I really doubt spammers are generating unique image files for every email they send so they can determine by the filename alone to whom they sent email. Instead they would use #3 where they use the same file but specify parameters on the retrieve to let their script record them and do the lookup (if they keep a table) or merely specify the victim's email address as a parameter (but perhaps encoded).

Personally I would rather NOT have the Image filter block emails because they had a link to external content. Most email clients already have that block function for external content. Alas, I am still using Outlook 2002 which does not have that block option. However, I use another anti-spam program which can simply nullify the <IMG> content rather than block it. It merely changes <IMG src=url ...> to <IMG xsrc=url ...>. src is a valid parameter name but not xsrc, so any HTML rendering will see an <IMG> tag but with no valid link to what it should retrieve. If I really do need to see that image, I can just look at the HTML source code and go find the xsrc parameters and use the URL in a browser. This affords the ability to score an e-mail if it has <IMG src=url> tags (and by how many of them), nullifies those tags without blocking the email (for those of us that don't have an email client that blocks external content), and I could find the URL because the email got received rather than blocked but was still made safe.

Blocking spam is great. However, sometimes I want to make my emails more safe while NOT blocking them. That isn't just for spam. That is for email from anywhere, including ham. Not all emails (and, in fact, few of mine) have web bugs, especially since other mechanisms are used to determine if the email is spam and to block/tag it.
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Registriert: 1. Feb 2008, 14:31

Re: Image filter: Trigger on any external linked content?

Beitragvon anbuva » 1. Nov 2009, 12:49

Hallo VanguardLH!

excuse the very, very, late answer, which can happen easily sometimes :oops: . It can be, that we have sometimes not any suitable answer to your question. I answer here now, however, so that your question will not forget and you also see that we take seriously every contribution.

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