WORM_DOWNAD.HG

 Analysis by: Anthony Joe Melgarejo

 ALIASES:

Worm:Win32/Conficker.B (Microsoft), W32.Downadup.B (Symantec), W32/Conficker.worm.gen.a (McAfee), Win32/Conficker.AC worm (ESET), Worm:W32/Downadup.BW (FSecure), Worm/Conficker.Z.14 (Antivir), Win32.Worm.Downadup.Gen (Bitdefender), Worm.Downadup-41 (ClamAV), W32/Conficker.A!worm (Fortinet), Worm.Win32.Conficker (Ikarus), W32/Conficker.C.worm (Panda),

 PLATFORM:

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

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


This worm may be dropped by other malware.

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

  TECHNICAL DETAILS

File Size:

169,043 bytes

File Type:

DLL

Memory Resident:

Yes

Initial Samples Received Date:

02 Jan 2014

Arrival Details

This worm may be dropped by other malware.

Other System Modifications

This worm adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\zrsfdtme

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_ZRSFDTME

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

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\zrsfdtme
ImagePath = "%System%\{number}.tmp"

It modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
Hidden = "2"

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

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

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced\Folder\Hidden\
SHOWALL
CheckedValue = "0"

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

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\BITS
Start = "4"

(Note: The default value data of the said registry entry is 3.)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\ERSvc
Start = "4"

(Note: The default value data of the said registry entry is 2.)

HKEY_CURRENT_CONFIG\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
ProxyEnable = "0"

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

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Hardware Profiles\0001\Software\
Microsoft\windows\CurrentVersion\
Internet Settings
ProxyEnable = "0"

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

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wscsvc
Start = "4"

(Note: The default value data of the said registry entry is 2.)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wuauserv
Start = "4"

(Note: The default value data of the said registry entry is 2.)

It creates the following registry entry(ies) to bypass Windows Firewall:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\GloballyOpenPorts\
List
{random port number}:TCP = "{random port number}:TCP:*:Enabled:mdqkva"

Propagation

This worm creates the following folders in all removable drives:

  • {removable drive}:\RECYCLER
  • {removable drive}:\RECYCLER\S-5-3-42-2819952290-8240758988-879315005-3665

It drops the following copy(ies) of itself in all removable drives:

  • {removable drive}:\RECYCLER\S-5-3-42-2819952290-8240758988-879315005-3665\jwgkvsq.vmx

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

The said .INF file contains the following strings:

;{garbage characters}
[AUTorUN
;{garbage characters}
AcTION=Open folder to view files
;{garbage characters}
icon=%syStEmrOot%\sySTEM32\sHELL32.Dll ,4
;{garbage characters}
shelLExECUte=RuNdLl32.EXE .\RECYCLER\S-5-3-42-2819952290-8240758988-879315005-3665\jwgkvsq.vmx,ahaezedrn
;{garbage characters}

Other Details

This worm connects to the following URL(s) to get the affected system's IP address:

  • http://www.whatismyip.org/
  • http://checkip.dyndns.org/
  • http://whatsmyipaddress.com

It connects to the following possibly malicious URL:

  • http://{pseudorandom domain}.cc
  • http://{pseudorandom domain}.cn
  • http://{pseudorandom domain}.ws
  • http://{pseudorandom domain}.com
  • http://{pseudorandom domain}.net
  • http://{pseudorandom domain}.org
  • http://{pseudorandom domain}.info
  • http://{pseudorandom domain}.biz

NOTES:

Upon execution, it opens a window which displays the files under the malware path's root drive to hide its malicious routines from the user. It modifies its file attributes to Read-only and Hidden after execution.

  SOLUTION

Minimum Scan Engine:

9.700

FIRST VSAPI PATTERN FILE:

10.516.02

FIRST VSAPI PATTERN DATE:

02 Jan 2014

VSAPI OPR PATTERN File:

10.517.00

VSAPI OPR PATTERN Date:

03 Jan 2014

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

Restart in Safe Mode

[ Learn More ]

Step 3

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.

  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    • zrsfdtme
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root
    • LEGACY_ZRSFDTME

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_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\GloballyOpenPorts\List
    • {random port number}:TCP = "{random port number}:TCP:*:Enabled:mdqkva"

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: Hidden = "2"
      To: Hidden = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: SuperHidden = "0"
      To: SuperHidden = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Folder\Hidden\SHOWALL
    • From: CheckedValue = "0"
      To: CheckedValue = "1"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\BITS
    • From: Start = "4"
      To: Start = "3"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\ERSvc
    • From: Start = "4"
      To: Start = "2"
  • In HKEY_CURRENT_CONFIG\Software\Microsoft\Windows\CurrentVersion\Internet Settings
    • From: ProxyEnable = "0"
      To: ProxyEnable = "1"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Hardware Profiles\0001\Software\Microsoft\windows\CurrentVersion\Internet Settings
    • From: ProxyEnable = "0"
      To: ProxyEnable = "1"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\wscsvc
    • From: Start = "4"
      To: Start = "2"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\wuauserv
    • From: Start = "4"
      To: Start = "2"

Step 6

Search and delete AUTORUN.INF files created by WORM_DOWNAD.HG that contain these strings

[ Learn More ]
;{garbage characters}
[AUTorUN
;{garbage characters}
AcTION=Open folder to view files
;{garbage characters}
icon=%syStEmrOot%\sySTEM32\sHELL32.Dll ,4
;{garbage characters}
shelLExECUte=RuNdLl32.EXE .\RECYCLER\S-5-3-42-2819952290-8240758988-879315005-3665\jwgkvsq.vmx,ahaezedrn
;{garbage characters}

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.
  • {removable drive}:\RECYCLER

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_DOWNAD.HG. 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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