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Backdoor.Win32.QUASAR.C

January 09, 2020
 ALIASES:

Backdoor:Win32/QuasarRAT.A (Microsoft); RDN/Generic PWS.y (McAfee); Trojan-Dropper.Win32.Dapato.qalu (Kaspersky); Troj/Subti-A (Sophos); Trojan.Win32.Generic!BT (Sunbelt)

 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


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.

  TECHNICAL DETAILS

File Size:

280,064 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

09 Jan 2020

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.

Installation

This Backdoor adds the following processes:

  • powershell -inputformat none -outputformat none -NonInteractive -Command Add-MpPreference -ExclusionPath "%System Root%\Users"
  • schtasks /create /sc minute /mo 5 /tn "Microsoft\SubDir\Subfile" /tr "%Application Data%\SubDir\Subfile.exe" /RL HIGHEST /f
  • %Application Data%\Loader.exe %Application Data%\Loader.exe -pP@$$W0RD#@
  • timeout 7
  • attrib +s +h %Application Data%\SubDir
  • attrib +s +h %Application Data%\logs
  • attrib +s +h /d /s
  • %System%\svchost.exe -k netsvcs
  • chcp 65001
  • %System%\PING.EXE ping -n 10 localhost
  • %Application Data%\Loader.exe

(Note: %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.. %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).. %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

Other System Modifications

This Backdoor deletes the following files:

  • %User Temp%\A11E.tmp\A12F.tmp\extd.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(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It deletes the following folders:

  • %User Temp%\A11E.tmp\A12F.tmp

(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(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

Dropping Routine

This Backdoor drops the following files:

  • %Application Data%\Loader.exe

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.850

Step 1

Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 users must disable System Restore to allow full scanning of their computers.

Step 2

Identify and terminate files detected as Backdoor.Win32.QUASAR.C

[ 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

Search and delete this file

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %Application Data%\Loader.exe

Step 4

Scan your computer with your Trend Micro product to delete files detected as Backdoor.Win32.QUASAR.C. 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 the following Trend Micro Support pages for more information:

Step 5

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

  • %User Temp%\A11E.tmp\A12F.tmp\extd.exe


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