Analysis by: Melvin Jhun Palbusa
ALIASES:

Win32:Adware-gen (AVAST)

 PLATFORM:

Windows

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

  • Threat Type: Potentially Unwanted Application

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

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

This Potentially Unwanted Application 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: 2,488,040 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 30 May 2023
Payload: Drops files

Arrival Details

This Potentially Unwanted Application 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 Potentially Unwanted Application drops the following files:

  • %User Temp%\nsscc87.tmp\ICommon.dll
  • %User Temp%\nsscc87.tmp\System.dll
  • %User Temp%\nsscc87.tmp\opt.dll
  • %Application Data%\xxtt\Opt.dll
  • %Application Data%\xxtt\uninst.exe
  • %Application Data%\xxtt\Update.exe
  • %Application Data%\xxtt\xxtt.exe
  • %Application Data%\Temp.dat
  • %Desktop%\{Random Characters}.lnk
  • %Programs%\{Random Characters].lnk
  • %Programs%\{Random Characters}.lnk

(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).. %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).. %Desktop% is the current user's desktop, which is usually C:\Documents and Settings\{User Name}\Desktop on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\Desktop on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).. %Programs% is the folder that contains the user’s program groups, which is usually C:\Windows\Start Menu\Programs or C:\Documents and Settings\{User name}\Start Menu\Programs on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Start Menu\Programs on Windows Vista, 7, and 8.)

It adds the following processes:

  • rundll32.exe "%User Temp%\nsscc87.tmp\ICommon.dll",ITerminateProcess_Rundll32 %Application Data%\xxtt
  • rundll32.exe "%Application Data%\xxtt\opt.dll", IRundll32_CustomStat {softType'8',keyUrl:'http://{BLOCKED}s.xiaoxintoutiao.com/'hrdhlktnew/' ,postUrl: 'http://{BLOCKED}s.xiaoxintoutiao.com/iwehjranew/ ',productChannel:",productVersion:'3.0.1903.372}

Other System Modifications

This Potentially Unwanted Application adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\App Paths\
xxt.exe
(Default) = %Application Data%\xxtt\xxtt.exe

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Uninstall\
xxtt
(Default) = (value not set)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Uninstall\
xxtt
DisplayIcon = %Application Data%\xxtt\xxtt.exe

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Uninstall\
xxtt
DisplayName = {Random Characters}

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Uninstall\
xxtt
DisplayVersion = 3.0.1903.372

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Uninstall\
xxtt
Publisher = {Random Characters}

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Uninstall\
xxtt
UninstallString = %Application Data%\xxtt\uninst.exe

HKEY_CURRENT_USER\Software\xxtt
(Default) = (value not set)

HKEY_CURRENT_USER\Software\xxtt
Channel =

HKEY_CURRENT_USER\Software\xxtt
gdcfg = 246da641b298d1a168f95e3f4f2b056700251795fcd5562546333b7592fbba0289116d5bc16f2623b29

HKEY_CURRENT_USER\Software\xxtt
InstallTime = {Current Date} 12:15:58

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
xxtt = %Application Data%\xxtt\xxtt.exe -mode:3

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer
GlobalAssocChangedCounter = 36

It adds the following registry keys as part of its installation routine:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\App Paths\
xxtt.exe

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Uninstall\
xxtt

HKEY_CURRENT_USER\Software\xxtt

Other Details

This Potentially Unwanted Application connects to the following possibly malicious URL:

  • {BLOCKED}s.xiaoxintoutiao.com

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 2.627.00
FIRST VSAPI PATTERN DATE: 31 May 2023
VSAPI OPR PATTERN File: 2.627.00
VSAPI OPR PATTERN Date: 01 Jun 2023

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

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

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.
  • %User Temp%\nsscc87.tmp\ICommon.dll
  • %User Temp%\nsscc87.tmp\System.dll
  • %User Temp%\nsscc87.tmp\opt.dll
  • %Application Data%\xxtt\Opt.dll
  • %Application Data%\xxtt\uninst.exe
  • %Application Data%\xxtt\Update.exe
  • %Application Data%\xxtt\xxtt.exe
  • %Application Data%\Temp.dat
  • %Desktop%\{Random Characters}.lnk
  • %Programs%\{Random Characters].lnk
  • %Programs%\{Random Characters}.lnk

Step 4

Delete this registry key

[ 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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

  • In HKEY_CURRENT_USER\Software\xxtt

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\App Paths\xxtt.exe

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Uninstall\xxtt

Step 5

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\App Paths\xxt.exe
    • (Default) = %Application Data%\xxtt\xxtt.exe
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Uninstall\xxtt
    • (Default) = (value not set)
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Uninstall\xxtt
    • DisplayIcon = %Application Data%\xxtt\xxtt.exe
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Uninstall\xxtt
    • DisplayName = {Random Characters}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Uninstall\xxtt
    • DisplayVersion = 3.0.1903.372
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Uninstall\xxtt
    • Publisher = {Random Characters}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Uninstall\xxtt
    • UninstallString = %Application Data%\xxtt\uninst.exe
  • In HKEY_CURRENT_USER\Software\xxtt
    • (Default) = (value not set)
  • In HKEY_CURRENT_USER\Software\xxtt
    • Channel =
  • In HKEY_CURRENT_USER\Software\xxtt
    • gdcfg = 246da641b298d1a168f95e3f4f2b056700251795fcd5562546333b7592fbba0289116d5bc16f2623b29
  • In HKEY_CURRENT_USER\Software\xxtt
    • InstallTime = {Current Date} 12:15:58
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • xxtt = %Application Data%\xxtt\xxtt.exe -mode:3
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer
    • GlobalAssocChangedCounter = 36

Step 6

Scan your computer with your Trend Micro product to delete files detected as PUA.Win32.Convagent.AA. 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:


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