Security researchers are warning of a new, easy-to-exploit email trick that could allow an attacker to turn a seemingly benign email into a malicious one after it has already been delivered to your email inbox.
Dubbed Ropemaker (stands for Remotely Originated Post-delivery Email Manipulation Attacks Keeping Email Risky), the trick was uncovered by Francisco Ribeiro, the researcher at email and cloud security firm Mimecast.
A successful exploitation of the Ropemaker attack could allow an attacker to remotely modify the content of an email sent by the attacker itself, for example swapping a URL with the malicious one.
This can be done even after the email has already been delivered to the recipient and made it through all the necessary spam and security filters, without requiring direct access to the recipient’s computer or email application, exposing hundreds of millions of desktop email client users to malicious attacks.
Ropemaker abuses Cascading Style Sheets (CSS) and Hypertext Markup Language (HTML) that are fundamental parts of the way information is presented on the Internet.
“The origin of Ropemaker lies at the intersection of email and Web technologies, more specifically Cascading Style Sheets (CSS) used with HTML,” Mimecast’s Senior Product Marketing Manager Matthew Gardiner writes in a blog post.
“While the use of these web technologies has made email more visually attractive and dynamic relative to its purely text-based predecessor, this has also introduced an exploitable attack vector for email.”
Since CSS is stored remotely, researchers say an attacker can change the content of an email through remotely initiated changes made to the desired ‘style’ of the email that is then retrieved remotely and presented to the user, without the recipient, even tech savvy users, knowing about it.
Source: The Hacker news