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EFAIL: detection and prevention

In our previous blog posting we discussed the EFAIL "Generic exfiltration" attack on S/MIME and suggested how such an attack may be detected.

Even though the CipherMail gateway is not directly vulnerable to EFAIL (see EFAIL: which is vulnerable? PGP, S/MIME or your mail client? for more details), if your email client is configured to automatically download external resources, your email client may leak your decrypted email.

The main issue with the EFAIL "Generic exfiltration" attack is that an encrypted message can be modified by an attacker without being detected. This is a general S/MIME problem and can only be solved by fixing the S/MIME standards.

Door admin|2024-09-30T07:42:09+00:00juni 28, 2018|Article, Artikel, Engels, Nederlands|Reacties uitgeschakeld

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EFAIL: how to detect you are being attacked?

In an earlier blog, we discussed some implications of the newly found EFAIL attack on PGP and S/MIME. We concluded that CipherMail gateway was not directly vulnerable because the gateway does not load remote content from the email. The email only gets decrypted, validated and then forwarded.

The EFAIL paper describes two types of attack. The "Direct exfiltration" attack and the "Generic exfiltration" attack.

Door admin|2024-08-26T14:16:10+00:00juni 14, 2018|Article, Artikel, Engels, Nederlands|Reacties uitgeschakeld

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EFAIL: which is vulnerable? PGP, S/MIME or your mail client?

What is EFAIL?

EFAIL is a recent attack on PGP en S/MIME email encryption (EFAIL).

EFAIL exploits remote content resolving built into most email clients (like for example images and CSS rules) to get (parts) of a previously encrypted email.

What EFAIL basically does, is that it takes a previously encrypted email (for which the attacker does not have the private key) and embeds this encrypted email into a new email in a special way. The email is then sent to the recipient for decryption. The attacker however designed the email in a way that the decrypted content of the original email gets embedded into the URL for a remote resource (for example an image). If the email client is configured to automatically resolve external content (for example download images), the content of the email gets sent to the remote server as a URL request. If the remote server is under control of the attacker, or if the URL is sent via HTTP, the attacker can access the URL and therefore has access to the plain text content of the original email.

Door admin|2024-02-17T12:37:32+00:00mei 31, 2018|Article, Artikel, Engels, Nederlands|Reacties uitgeschakeld

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