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PUA.Win32.FlashServ.U

June 13, 2022
 ALIASES:

HEUR:AdWare.Win32.FlashServ.gen (KASPERSKY)

 PLATFORM:

Windows

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

  • Threat Type: Potentially Unwanted Application

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

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.

It connects to certain websites to send and receive information.

  TECHNICAL DETAILS

File Size:

1,127,928 bytes

File Type:

EXE

File Compression:

UPX

Memory Resident:

Yes

Initial Samples Received Date:

03 Jun 2022

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 file(s)/component(s):

  • %System%\Macromed\Flash\flashupdater.cfg

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

It creates the following folders:

  • %System%\Macromed

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

Autostart Technique

This Potentially Unwanted Application registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\{CurrentControlSet|ControlSet001}\
services\Flash Helper Service
ImagePath = {Malware path and name}

Other System Modifications

This Potentially Unwanted Application adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\miniconfig
guid = {9BC39906-31C7-48e4-86D5-85DEF04CD690}

HKEY_LOCAL_MACHINE\SOFTWARE\Macromedia\
FlashHelper
ueip = {number}

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\miniconfig
ueip = {number}

HKEY_LOCAL_MACHINE\SOFTWARE\Macromedia\
FlashHelper
active = {Current Date}

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
AppID\{B9020634-CE8F-4F09-9FBC-D108A73A4676}
LocalService = Flash Helper

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\miniconfig
open_mini_time = {value}

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\miniconfig
mini_count = {value}

Other Details

This Potentially Unwanted Application adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Macromedia

HKEY_LOCAL_MACHINE\SOFTWARE\Macromedia\
FlashHelper

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\miniconfig

HKEY_USERS\.DEFAULT\Software\
Microsoft\Windows\CurrentVersion\
miniconfig

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
AppID\{B9020634-CE8F-4F09-9FBC-D108A73A4676}

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Uninstall\
FlashCenter

It connects to the following website to send and receive information:

  • https://api.{BLOCKED}h.cn/config/powerBoot?rc={value}&helper=2.3.0.73&
  • https://api.{BLOCKED}h.cn/config/getBin?helper=2.3.0.73&key={value}
  • https://tongji.{BLOCKED}h.cn/hm2.gif?msgtype=helperdata={Hex values}&token={Hex values}&time={Hex values}
  • https:/tongji.{BLOCKED}h.cn/hm4.gif?product=hs&event=fcad&uid={ID}&um={Hex values}&platform={platform}&channel={value}&version={app version}&signature={Hex values}&key={value}&data={Hex values}

It does the following:

  • It listens on the following ports:
    • 21440
    • 21441

It accepts the following parameters:

  • /install - registers itself as a service
  • /start - starts registered service
  • /uninstall - deletes registered service

  SOLUTION

Minimum Scan Engine:

9.800

SSAPI PATTERN File:

2.521.00

SSAPI PATTERN Date:

09 Jun 2022

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

Restart in Safe Mode

[ Learn More ]

Step 4

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\miniconfig
    • guid = {9BC39906-31C7-48e4-86D5-85DEF04CD690}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Macromedia\FlashHelper
    • ueip = {number}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\miniconfig
    • ueip = {number}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Macromedia\FlashHelper
    • active = {Current Date}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\AppID\{B9020634-CE8F-4F09-9FBC-D108A73A4676}
    • LocalService = Flash Helper
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\miniconfig
    • open_mini_time = {value}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\miniconfig
    • mini_count = {value}

Step 5

Delete this registry key

[ Learn More ]

=Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator’s help. You may also check out this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SYSTEM\{CurrentControlSet|ControlSet001}\services\Flash Helper Service
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Macromedia
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Macromedia\FlashHelper
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\miniconfig
  • In HKEY_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\miniconfig
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\AppID\{B9020634-CE8F-4F09-9FBC-D108A73A4676}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Uninstall\FlashCenter

Step 6

Search and delete these files

[ 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.
  • %System%\Macromed\Flash\flashupdater.cfg

Step 7

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %System%\Macromed

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as PUA.Win32.FlashServ.U. 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.


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