Vulnerabilities patched earlier this year in Firefox and Internet Explorer have been exploited by an advanced persistent threat (APT) actor in attacks aimed at China and Japan.
The Firefox vulnerability is CVE-2019-17026, which Mozilla patched in early January, and the Internet Explorer flaw is CVE-2020-0674, which Microsoft patched in February with its monthly security updates. Both vulnerabilities were exploited in attacks before patches were released.
A blog post published in February by Chinese cybersecurity firm Qihoo 360 revealed that both security bugs were exploited as part of the same campaign aimed at Chinese government agencies.
Qihoo 360 has attributed the attacks to the threat actor named DarkHotel, which the company tracks as APT-C-06. Qihoo says the group operates from East Asia and refers to it as the “Peninsula APT,” which could be a reference to the Korean Peninsula. Others previously linked DarkHotel to South Korea.
Japan’s Computer Emergency Response Team Coordination Center (JPCERT/CC) has reported seeing attacks on Japanese entities exploiting both CVE-2019-17026 and CVE-2020-0674.
In a blog post published on Thursday, JPCERT said targeted users are taken to a website set up to deliver Firefox or Internet Explorer exploits depending on the victim’s browser. If the exploit is successful, a proxy auto-configuration (PAC) file is downloaded to the system. These PAC files can allow attackers to redirect requests made to specified websites through an external server they control.
Ultimately, a piece of malware known as Gh0st RAT was downloaded to the victim’s system in the attacks observed by the Japanese agency. Gh0st RAT has often been used by threat actors linked to China, but the malware’s source code was leaked many years ago and anyone could be using it these days.
JPCERT noted that the malware only gets executed on 64-bit Windows 7 and Windows 8.1 devices, but it does not appear to work on Windows 10. It’s worth pointing out that Microsoft’s advisory said exploitation against both older and the latest software releases had been detected.
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