Hackers hit Hong Kong church site using just patched IE zero-day

A day after Microsoft released a patch for critical bug in Internet Explorer researchers have found it being used in semi-targeted attacks on visitors to a church in Hong Kong.

The patch, released yesterday, addressed a remote memory corruption bug in all supported versions of IE that could leave users exposed to attacks via a specially crafted website. Microsoft noted the bug was already being actively targeted online at the time, suggesting that attackers already knew about it at the same time as the Google researcher who reported it Microsoft.

Security firm Symantec on Wednesday said that its telemetry data revealed the newly patched flaw was being used in attacks targeting visitors to the website of the Evangelical Lutheran Church of Hong Kong.

The church’s site had been compromised to automatically redirect visitors to another website that hosted an exploit for the IE bug, known as CVE-2015-2502.

Symantec has dubbed the hack a “watering hole attack” since it targets visitors with a particular profile, though it’s not clear to who church’s visitors would be of interest nor why.

However, Symantec noted that the remote access trojan (RAT) delivered to visitors is known as Korplug (which is also called PlugX) — a tool has been seen in , typically on targets in Asia, in combination with IE and Flash Player zero day exploits.

Researchers at online rights group Citizen Lab earlier this year new tactics used in surveillance campaigns involving PlugX that targeted Tibetan groups and pro-democracy groups in Hong Kong, however it mostly relied on a Windows bug from 2014 and rigged PowerPoint attachments.

The website that IE users are redirected to “hosts a file called vvv.html , which redirects to one of two other files called a.js and b.js, which lead to the download of a file called java.html to the victim’s computer. Java.html installs Korplug on the computer, in the form of an executable called c.exe,” explained Symantec.

Rival security firm ESET last year traced the Korplug/PlugX RAT to spy campaigns targeting military organisations in Afghanistan and Tajikistan as well as several high-profile organisations in Russia. According to it, the Korplug tool has been linked to a professional Chinese hacking group and used in targeted attacks since 2012.

Want to know more?

Why not become a CSO member and subscribe to CSO's mailing list. 

Get newsletters, updates, events and more right here