A newly identified malware attack campaign has been exfiltrating emails from targeted organizations using a JavaScript backdoor injected into a webmail system widely used in Taiwan.
According to an advisory from Trend Micro, the attacks are linked to Earth Wendigo, a threat actor that does not appear to be affiliated with known hacking groups.
Starting May 2019, Trend Micro said Earth Wendigo has been targeting multiple organizations, including government entities, research institutions, and universities in Taiwan.
The attacks include the use of spear-phishing emails to various targets, including politicians and activists linked to Tibet, the Uyghur region, or Hong Kong.
As an initial attack vector, the group used spear-phishing emails containing obfuscated JavaScript code meant to load malicious scripts from an attacker-controlled remote server.
These scripts were designed to steal browser cookies and webmail session keys, propagate the infection by appending code to the victim’s email signature, and exploit a cross-site scripting (XSS) vulnerability in the webmail server for JavaScript injection.
The exploited XSS vulnerability resides in the webmail system’s shortcut feature and allows the attackers to add a shortcut with a crafted payload, replacing parts of the webmail system’s page with malicious JavaScript code.
Trend Micro reported that the XSS vulnerability was fixed in January 2020, meaning that only organizations that haven’t updated to the latest version of the webmail server remain exposed.
Should this method fail, the attackers’ script registers malicious JavaScript code to the server’s Service Worker (a programmable network proxy inside the browser), so that it could intercept and manipulate HTTPS requests, hijack login credentials, and add malicious scripts to the webmail page.< ..
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