It shouldn't be a big surprise to hear that phishing is a big problem for banks. Criminals send email pretending to be a bank, and set up web sites that look a lot like a bank. One reason that phishing is possible is that e-mail has no built in security, so that if a mail message comes in purporting to be from, say, email@example.com, there's no easy way to tell whether the message is really from bankofamerica.com, or from a crook.
Mail authentication schemes like DKIM and the new dmarc.org group use cryptographic signatures to help authenticate mail and prove that it really is from who it purports to be from. So, if the mail can authenticate the sender, the phishing problem goes away, right?
Unfortunately not. One huge problem is that even if you have all the crypto stuff so you can be 100% sure that a message really is from, say, BANK-AMERICA.COM, you don't know whether BANK-AMERICA.COM is actually your bank or not.
Then see if you can figure out why a bank would use over a thousand different domains. My example here is Bank of America, but they're no worse than other big banks; I picked them because their name is easy to search for.
If banks were serious about phishing, they'd pick one name, one domain, and use that consistently. But they don't.
PS: BANK-AMERICA.COM belongs to some guy in France.
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