A Tale of PivNoxy and Chinoxy Puppeteer

The attack started with a simple email that included a bare document as an attachment “please help to check.doc”
The attached doc file is in RTF format.
It was generated using a tool called Royal Road, a phishing “weaponizer” believed to be used by several Asia-based APT threat actors.
Also referred to as 8.t RTF exploit builder, Royal Road allows APT groups to create RTF files with embedded objects that can exploit vulnerabilities in Microsoft Word to infect targets.
Some of the known vulnerabilities that Royal Road supports include:

CVE-2017-11882 (Microsoft Office Memory Corruption Vulnerability)
CVE-2018-0802 (Microsoft Office Memory Corruption Vulnerability)
CVE-2018-0798 (Microsoft Office Memory Corruption Vulnerability)

Opening the email attachment, “Please help to CHECK.doc,” opens a decoy Word document.
And at the same time, it exploits CVE-2018-0798 in the background.
CVE-2018-0798 is a Remote Code Execution (RCE) vulnerability in Microsoft’s Equation Editor (EQNEDT32).
Microsoft released a fix for it on January 9, 2018.
The fact that attackers are still targeting this vulnerability highlights that not all organizations deploy critical patches or upgrade to the latest software.
The truth is that older vulnerabilities are still commonly and successfully being exploited.
Once executed, the malicious document drops three files:

C:\ProgramDataCannonCannondriver.exe
C:\ProgramDataCannonLBTServ.dll
C:\ProgramDataCannonMicrosoft.BT
Despite the deceptive file name, the Cannondriver.exe file is a legitimate Logitech file, LBTWizGi.exe, with the description, “Logitech Bluetooth Wizard Host Process.” The Cannondriver.exe is even digitally signed by a certificate issued to Logitech.

on the other hand, the LBTServ.dll file is not digitally signed.
This is where it gets interesting.

“Cannondriver.exe” is vulnerable to a DLL Search Order Hijacking attack that LBTServ.dll takes advantage of.
Take note that the “LBTServ.dll” sample used in this attack has a compilation time of Sun July 18 02:04:24 2021 GMT.
This means that this group created this variant well before they needed to use it.
It suggests they were either ready to attack their target almost a year before or had started stockpiling an arsenal of malware ready to go at a moment’s notice.
Recent Chinoxy samples that stayed under the radar, but were uncovered during our investigation, have similar compile times.

After Cannondriver.exe loads the fake LBTServ.dll and calls the LGBT_Launch function, the malicious function loads the other dropped file, Microsoft.BT, into memory and proceeds to decrypt it.
The attack chain is similar to that used by the Chinoxy backdoor, which also uses Cannondriver.exe to load a malicious LBTServ.dll to deliver its payload.