Kaspersky believes the attackers compromised the bank’s account at Registro.br. That’s the domain registration service of NIC.br, the registrar for sites ending in the Brazilian .br top-level domain, which they say also managed the DNS for the bank. With that access, the researchers believe, the attackers were able to change the registration simultaneously for all of the bank’s domains, redirecting them to servers the attackers had set up on Google’s Cloud Platform.
With that domain hijacking in place, anyone visiting the bank’s website URLs were redirected to lookalike sites. And those sites even had valid HTTPS certificates issued in the name of the bank, so that visitors’ browsers would show a green lock and the bank’s name, just as they would with the real sites. Kaspersky found that the certificates had been issued six months earlier by Let’s Encrypt, the non-profit certificate authority that’s made obtaining an HTTPS certificate easier in the hopes of increasing HTTPS adoption.
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