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full-disclosure-uk: Re: [Full-disclosure] simple phishing fix

Re: [Full-disclosure] simple phishing fix

From: Nick FitzGerald <nick_at_nospam>
Date: Tue Jul 29 2008 - 08:12:42 GMT
To: full-disclosure@lists.grok.org.uk

lsi wrote:

> Of all the approaches below I like the simple list of strings in the
> email client (the first link). This is because it's a DENY ALL
> policy. ...

"simple" -- yes.

"DENY ALL" -- nope...

>From your first post, it's clear that you receive samples from a _VERY_
limited sliver of the bank, credit union and other financial target phishing that goes on each and every day...

>From a purely theoretical perspective, to make your preferred approach
"DENY ALL" you would have to have ongoing access to an oracle identifying the domains of ALL financial institutions, so your block list could be updated in a timely manner as domains are added and removed...

As no such oracle exists, a "deny all" approach along the lines you suggest is _practically_ impossible.

> ... The other approaches below, AFAICS, use ACCEPT ALL and then
> try and find reasons to block the mail. ...

Which is actually what your suggested approach does, even if it could be practically implemented -- it accepts all Email (or at least all incoming Email delivery connections) then tries to find a reason to block it (From address domain on block list).

> ... The first approach simply
> blocks them all! ...

...for some interesting and unknowably odd value of "all".

> ... Sure, you want to receive mail from the Bank of
> Foo, just don't put bankoffoo.com in your list!

Thereby letting through the phish for the target(s) of most danger to you -- get suckered by a Foo Bank phish as a Foo Bank customer and you may be in trouble, but getting suckered by a Bar Bank phish when you are only a Foo Bank customer and no harm is done.

Also, your preferred approach entirely fails to deal with "close but not quite" domain "spoofing" -- info@vvachovia.com rather than info@wachovia.com, suport@foo_bank.com rather than support@foo-bank.com (the real Foo Bank domain), etc, etc, etc.

In short, as is commonly the case in such matters, the quick'n'dirty, I- -thought-of-the-ultimate-solution-to-the-phishing-problem-AND-it's- -SIMPLE solution is so far from complete that it's all but useless...


Nick FitzGerald

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