Analysis by: Abraham Latimer Camba


Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)


  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes


Infection Channel: Downloaded from the Internet, Dropped by other malware

This malware is related to the targeted attacks leveraged against a top US government organization on December 2012. It was sent through an email claiming to be from the Syrian government. It allows the attackers to execute remote commands on the affected system, which can result in the system's security (and any information held within) being compromised.

To get a one-glance comprehensive view of the behavior of this Backdoor, refer to the Threat Diagram shown below.

For the related story, you may read the blog post QUARIAN Attacks Expand their Target

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It executes commands from a remote malicious user, effectively compromising the affected system.


File Size: Varies
File Type: EXE, PE
Memory Resident: Yes
Initial Samples Received Date: 04 Dec 2012
Payload: Collects system information, Compromises system security, Downloads files

Arrival Details

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.


This backdoor drops the following copies of itself into the affected system and executes them:

  • %User Temp%\update.exe

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • windowsupdataguoDL

Autostart Technique

This backdoor adds the following registry entries to enable its automatic execution at every system startup:

wintinfo.exe = "%User Temp%\update.exe"

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

  • Perform remote shell
  • Upload file to C&C server
  • Download file from C&C server
  • Execute files
  • Enumerate files and folders
  • Move files
  • Delete files
  • Change C&C connection delay
  • Delete the autorun registry entry HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run alg
  • Send the following information:
    • Host name
    • IP address
    • OS version information
    • User name
    • User privelege information

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • {BLOCKED}reddy1.{BLOCKED}


It tries to execute the following files:

  • %User Temp%\Readme.pdf


Minimum Scan Engine: 9.300
VSAPI OPR PATTERN File: 9.571.00
VSAPI OPR PATTERN Date: 05 Dec 2012

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Identify and terminate files detected as BKDR_QUARIAN.SM

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 3

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • wintinfo.exe = "%User Temp%\update.exe"

Step 4

Scan your computer with your Trend Micro product to delete files detected as BKDR_QUARIAN.SM. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.

Did this description help? Tell us how we did.