How is that spam coded? Spammers workaround

Subject: Viagra. But is really: bV a IAGR y A

[silverbytes]

I was suprised to receive a spam with subject "Viagra" because is there a filter to avoid that runing.

Then discovered that the text, that appears as "Viagra" is really "bV a IAGR y A"

How do they do that? And How do you filter that?

[physics]

Interesting, I often read email in pine (plain text) and see the 'V bx IAG y R A' type stuff but didn't realize those showed up as the actual word in some viewers. My guess is they use some sort of windows special characters that show up in the plain text but not in the subject line of outlook...

[dragonthoughts]

The extra characters are present to defeat trivial filtering rules.

A common trick is to have a plain text version and an HTML variant of the email (many clients send this way too). Most email clients display the "richer" HTML by default.

The extra characters are hidden using the HTML, or CSS, so that the majority of recipients will read their content.

The plain text version and the HTML version must be substantially identical in appaernt content, or some filtering programs will realise the discrepency and block the content.

[Quadrille]

They vary them all the time; each new form rapidly gets reported and added to filters.

I haven't had a v spam in my mailbox for months - they all go straight to my spam box.

But gmail filters are much better than most, as spam reports actually get used to develop the filters.

What kind of idiot buys chalk dust labelled as v anyway? Do they really still catch a single moron?

Seems hard to believe :)