Sophisticated DownEx Malware Campaign Targeting Central Asian Governments


May 10, 2023Ravie LakshmananMalware / Cyber Attack

DownEx Malware

Government organizations in Central Asia are the target of a sophisticated espionage campaign that leverages a previously undocumented strain of malware dubbed DownEx.

Bitdefender, in a report shared with The Hacker News, said the activity remains active, with evidence likely pointing to the involvement of Russia-based threat actors.

The Romanian cybersecurity firm said it first detected the malware in a highly targeted attack aimed at foreign government institutions in Kazakhstan in late 2022. Subsequently, another attack was observed in Afghanistan.

The use of a diplomat-themed lure document and the campaign’s focus on data exfiltration suggests the involvement of a state-sponsored group, although the exact identity of the hacking outfit remains indeterminate at this stage.


The initial intrusion vector for the campaign is suspected to be a spear-phishing email bearing a booby-trapped payload, which is a loader executable that masquerades as a Microsoft Word file.

Opening the attachment leads to the extraction of two files, including a decoy document that’s displayed to the victim while a malicious HTML application (.HTA) with embedded VBScript code runs in the background.

The HTA file, for its part, is designed to establish contact with a remote command-and-control (C2) server to retrieve a next-stage payload. While the exact nature of the malware is not unknown, it’s said to be a backdoor to establish persistence.

DownEx Malware

The attacks are also notable for employing a variety of custom tools for carrying out post-exploitation activities. This includes –

  • Two C/C++-based binaries (wnet.exe and utility.exe) to enumerate all the resources on a network,
  • A Python script ( to establish an infinite communication loop with the C2 server and receive instructions to steal files with certain extensions, delete files created by other malware, and capture screenshots, and
  • A C++-based malware (diagsvc.exe aka DownEx) that’s chiefly designed to exfiltrate files to the C2 server

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Two other variants of DownEx have also been earthed, the first of which executes an intermediate VBScript to harvest and transmit the files in the form of a ZIP archive.

The other version, which is downloaded via a VBE script (slmgr.vbe) from a remote server, eschews C++ for VBScript, but retains the same functionality as the former.

“This is a fileless attack – the DownEx script is executed in memory and never touches the disk,” Bitdefender said. “This attack highlights the sophistication of a modern cyberattack. Cybercriminals are finding new methods for making their attacks more reliable.”

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