We do believe Email is like a physical letter once it dropped it cannot be changed,but it is not true anymore here you can see a new technique called ROPEMAKER.
Security Researcher Francisco Ribeiro from Mimecast discovered a new attack pattern Dubbed ROPEMAKER used by attackers to remotely change the content that you see in your email.
ROPEMAKER stands for Remotely Originated Post-delivery Email Manipulation Attacks which allows changing the content of Email after post delivery even if they use S/MIME or PGP for signing.
Ropemaker originates between the intersection of email and web technologies.Web technologies introduced in Email to make it more dynamic which also leads to this attack vector.
As we aware CSS is a markup language to apply styles for a webpage and ROPEMAKER taking complete advantage of this including aspects such as the layout, colors, and fonts.
Two Sorts of ROPEMAKER Assaults
ROPEMAKER acts as long as the email client automatically connects to the remote CSS to retrieve the desired “style” for the email. This is at the core of the ROPEMAKER exploit.
Switch code method enables attackers to toggle the display between the good and bad URL’s portions in the Email.
Attackers can use this method to launch a cyber attack, let’s consider they could send an Email with two links one with good and bad one. Initially, they show the good link to Bypass the Organization security layers and then they change to the bad link.
The second method is even more sophisticated than Switch Exploit.Francisco Ribeiro says with this method, a comprehensive matrix script embedded sent by the attacker and then he displays whatever he wants by using use remote CSS.
For instance, he can display a blank Email and by simply changing the file he can display the message.
The attacker’s goal, in fact, is to avoid the target organization’s security controls and to deliver a malicious email which will be acted on by the targeted person.To download Technical paper presented by Francisco Ribeiro.
Danger with ROPEMAKER weakness
It is evident that it giving remote control for attackers to direct users to malicious websites and to bypass organization security layers.
PGP, S/MIME or DKIM doesn’t control because this cryptology manipulates only the content of the email but with ROPEMAKER there is no change in the content.It is just to decide what to display for recipients.
Ribeiro suggests to disable HTML version of mail and to use only plain text or you can switch over Webmail clients such as Gmail or outlook.