mailing list archives
Re: simple phishing fix
From: Nick FitzGerald <nick () virus-l demon co uk>
Date: Wed, 30 Jul 2008 21:27:45 +1200
Thank you all for your comments. However, I cannot disagree more
Ignorance does that for people...
It doesn't matter that the blacklist is not complete, if a scammer
tries to phish a bank that's not on the list, eg. is not popular, he
won't make much money, because it's a small bank and the probability
of him hitting an email address which works, and is an address of a
customer of that tiny bank, and the customer gets suckered, and all
other security mechanisms fail, is very small.
So, the spammer just sends _A LOT MORE_ phishing spam targetting that
There are US credit unions with only a few tens of thousands of customers
that have been targets of (LARGE) phishing campigns. The phishers in at
least some of those cases got several, to several dozen, known victims
and helped themselves to the contents of their accounts, in the few hours
between the beginning of the spam run and the CU becoming aware of it and
disabling their online banking interface. Those few successful targets
were more than reward enough...
And I once got a phishing scam Email for a small US bank that only had
_two_ physical branches according to the real bank's website (and no,
they weren't a large "mostly online" bank but an old-style, small-town,
Oh -- and those were _BEFORE_ some of the much more highly targetted, and
thus _MUCH_ smaller phishing spam runs we have seen more recently.
As you do not understand how these folk work, what a triflingly small
successful victim rate they have to hit for their effort to be
worthwhile, and so on, you are going to keep making the dumb-ass n00b
mistakes in your reasoning that we've been seeing from you for the last
Phishing still exists _BECAUSE_ it is a hard problem to solve.
Not because those who know how it works are lazy.
Not because those who know how it works are stupid.
Not because some, or even many, of those who know how it works are
employed by companies that a conspiracy theorist will ignorantly argue
have a vested interest in NOT solving the problem.
No -- phishing still exists _BECAUSE it is a hard problem to solve_.
If widely implemented, your trivial suggestions might, _just might_, ever
so slightly reduce the total world-wide cost of bank losses due to
But they would do so at a significantly greater cost in the effort
required to implement your suggestions across the planet than they would
save. Yes, the banks will spend a lot of money failing to entirely stamp
out phishing, BUT they generally try to spend that money in ways that at
least have some pay-off in terms of reassuring their customers that they
are doing something to help...
So, can you guess why your suggestions have not already been implemented?
The scammer knows this and so he targets the popular banks.
Nope -- the scammers target pretty much any and every bank they can be
bothered targeting. Yes -- the pre-packaged scams centre on the bigger
targets, but those are probably not the bigger scammers in terms of
actual impact -- I mean, a skiddie too stupid to know or be able to work
out that the "free" phishing kits (that he has just downloaded off a more
or less open web site) are backdoored and also sending his phished data
to someone else is not goingto be a major figure in the underworld scam
And as further evidence of the breadth of opportunity scammers are
prepared to deploy/employ, just this afternoon I uncovered a single
phishing site hosting eleven different UK-only banks involving close to
1.5MB of phishing site code, images, scripts, etc, etc to fake the eleven
target banks' sites.
Therefore, the blacklist only needs to contain popular banks.
However there is almost no penalty to add another 500 to the list,
it's a simple filter, it's fast.
I do agree that the more banks on the list, the better, but there are
not millions of banks in the world, it's not a problem to list all
the major banks, and many of the smaller banks as well.
Off you go then -- list 10% of the bank domains by this time tomorrow...
As the blacklist is deployed, the average revenue per mail (ARPM)
will fall. The more it is deployed, the more the ARPM will fall.
The ARPM does not need to hit zero. As soon as the ARPM falls below
the average cost to send each mail, phishing will be economically
As virtually all (phishing) spam is sent by "criminal gangs" using their
own bot-nets effectively for free, your simple view of the economics of
this fails rather badly.
History has a lesson for us here -- as the amount of spam-filtering in
use increased, so did the amount of spam being sent. If your economics
argument had any validity that should not be the case, but what happened
is that the spammers and associated scammers coalesced _AND_ changed hwo
they sent the vast bulk of their spam. Now, sending spam is essentially
free for sufficiently "big fish" in the underground spam community.
Eg. it might still be technically feasible, however it will no longer
be profitable to be a phisher.
It will profitable until (vitually) no-one _EVER_ reponds to _ANY_ spam.
Repeat, phish do not need to be completely eliminated. Once they are
reduced below a certain level, it will become economically infeasible
to be a phisher. The invisible hand  will do the rest of the work
I know of a nice bridge you may be interested in buying...
I agree that by opening a hole in your phish firewall (eg. permitting
traffic from the Bank of Foo) you are making yourself slightly less
protected, however if a user has a blacklist where he has to
specifically ALLOW traffic from a certain bank that user will be well
aware that he has opened a hole in his phish wall and will be
extremely attentive when he actually gets a mail. (I'm appalled that
You really have no f*&ing clue how "ordinary users'" tiny little brains
work, have you???
some banks actually use email, how cheap are they? If my bank did
that, I'd complain, and consider changing banks.) As with a real
firewall, it's not a total solution, but one layer of several.
Your "solution" will only help people who don't need it. It will leave
the low-hanging fruit just as numerous and just as close to ground...
The blacklist catches variations, of course the common variations are
listed as well, ...
Oh, so we need some additional infrastructure to make this a dynamically
(self)-updating blacklist mechanism.
That works across all manner of Email clients.
Maybe someone should productize this -- oh, wait...
... again, every combination is not required, because the
probabilities of failure rapidly stack up once the scammers start to
get too imaginative with their variations (eg. they will have to use
more and more obscure variations, which will trick less and less
users). I hear unicode will make life interesting, I'm looking
forward to some samples.
It's the low-hanging fruit thing.
More than enough users are gullible enough to click on URLs in Email
claiming to be from PayPal, say, that clearly some from gmail.com, say,
addresses, _and then fill in all their identity details at, say,
Those folk will still be just as readily targetted by all the phish that
totally evade your silly little scheme, _JUST AS THEY ARE NOW_.
If you don't understand the problem -- and you clearly don't -- I doubt
you're going to some up with (even a smallpart of) "the solution".
Blacklists do work. They are successfully used in many applications,
the Spamhaus blocklist, the denyhosts SSH tool and desktop AV
software all spring to mind. Blacklists don't work *when the content
they are checking is polymorphic*. Phish, by definition are NOT
polymorphic. We are talking banks here, they do not change their
names very often.
As already explained, you're attributing far too much nouse to the
typical victim of the phish we're already seeing today...
I think that is an important point. The problem space is a lot
smaller once you start working with a finite list of domainnames. A
blacklist is feasible in these circumstances.
It's the infinite set of domain names (and simple IP-only phishing spam
and websites) completely unrelated to your view of the apparently
desirable phishing target domains' names that cause most of the problems
Hoiw does your plan address them?
Oh, that's right -- you don't understand that they are bulk of the
problem set, so they're not even considered for consideration...
I agree my list is small, you'll note however it contains most of the
biggest banks, I didn't choose them, they self-selected, by being
sent to me. That's why they are the biggest banks, because the
scammers target those banks. There's obviously no reason why the
list could not contain every large bank in the world. I could maybe
hunt down some stats to add banks I don't get phished for, but that
would just slow down my filter! If others were to use it they'd want
to customise it. Because the blacklist is on the client machine, the
user is free to add banks they get hammered with, and free to remove
banks they want to correspond with.
_IF_ we could depend on the end users to do this updating, we wouldn't
have a phishing problem.
Your failure to understand the nature of the problem undermines your
Don't forget that "achovia." can be listed, to catch wachovia.com,
vvachovia.com, vvachovia.co.uk etc.
But not WA(HOVIA.COM, nor WACH0VIA.COM, nor WACHOVIA.C0M, nor
WACHOV1A.COM nor WACHO\/IA.COM, etc, etc. How many permutations are
there? For this one domain name?
Think about it, most people have no need to accept mail from every
bank in the world. That is accept ALL. Using the blacklist means
they are now denying all bank traffic. (OK, denying all on the list,
I agree that it's not a complete deny all, because we cannot know the
names of all banks in advance. I do regret confusing the discussion
by mentioning DENY ALL, I was hoping to explain my analogy to a
firewall, eg., it blocks everything by default and then lets in what
you tell it to let in, I do accept that unlike a real firewall it can
be got around by using an unlisted name, it's really DENY MOST.)
"(x) Mailing lists and other legitimate email uses would be affected
Irrelevant. They are affected already. They are the victims of
spoofing. It's either block their mails, or users suffer the spoofs.
Given than suffering the spoofs means bank-originated mails are
useless in any case, that means the only available course of action
is to deny all bank email traffic.
my Bayesian filter gets these anyway
My spam filter misses some, hence my post, however following this
comment I have checked my config and the Bayesian plugin is disabled
;) Thank you for the suggestion.
Full-Disclosure - We believe in it.
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Re: simple phishing fix Glenn.Everhart (Jul 29)
- Re: simple phishing fix, (continued)