Analysis by: Sabrina Lei Sioting

 ALIASES:

Worm:Win32/Mywife.E@mm (Microsoft), Email-Worm.Win32.Nyxem.e, Email-Worm.Win32.Nyxem.e (Kaspersky), W32.Blackmal.E@mm (Symantec), W32/MyWife.e@MM (McAfee), W32/Nyxem-D (Sophos), Win32.Nyxem.E@mm (Fsecure), Email-Worm.Win32.Mywife.gen (Sunbelt), Worm/Nyxem.E (Antivir), Win32.Nyxem.E@mm (Bitdefender), Email-Worm.Win32.Nyxem.E (Ikarus),

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW


This worm arrives as attachment to mass-mailed email messages. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

It propagates via shared networks and drops copies of itself into available networks.

  TECHNICAL DETAILS

File Size: 95,744 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 12 Mar 2008

Arrival Details

This worm arrives as attachment to mass-mailed email messages.

It may arrive via network shares.

It 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%\WINZIP_TMP.exe
  • %System Root%\Documents and Settings\All Users\Start Menu\Programs\Startup\WinZip Quick Pick.exe
  • %Windows%\Rundll16.exe
  • %Windows%\WINZIP_TMP.exe
  • %System%\scanregw.exe
  • %System%\Update.exe
  • %System%\Winzip.exe

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.. %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.. %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

It drops the following files:

  • %System%\{malware name}.zip
  • %System%\MSWINSCK.OCX

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

It uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
ScanRegistry = "scanregw.exe /scan"

Other System Modifications

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

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Licenses
{default} = "Licensing: Copying the keys may be a violation of established copyrights."

It modifies the following registry key(s)/entry(ies) as part of its installation routine:

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

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
CabinetState
FullPath = "1"

(Note: The default value data of the said registry entry is 0.)

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

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Licenses\096EFC40-6ABF-11cf-850C-08002B30345D

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Licenses\096EFC40-6ABF-11cf-850C-08002B30345D

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Licenses\190B7910-992A-11cf-8AFA-00AA00C00905

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Licenses\2c49f800-c2dd-11cf-9ad6-0080c7e7b78d

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Licenses\4250E830-6AC2-11cf-8ADB-00AA00C00905

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Licenses\4D553650-6ABE-11cf-8ADB-00AA00C00905

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Licenses\556C75F1-EFBC-11CF-B9F3-00A0247033C4

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Licenses\57CBF9E0-6AA7-11cf-8ADB-00AA00C00905

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Licenses\5f54e750-ce26-11cf-8e43-00a0c911005a

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Licenses\6FB38640-6AC7-11cf-8ADB-00AA00C00905

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Licenses\72E67120-5959-11cf-91F6-C2863C385E30

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Licenses\78E1BDD1-9941-11cf-9756-00AA00C00908

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Licenses\7C35CA30-D112-11cf-8E72-00A0C90F26F8

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Licenses\899B3E80-6AC6-11cf-8ADB-00AA00C00905

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Licenses\9E799BF1-8817-11cf-958F-0020AFC28C3B

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Licenses\B1EFCCF0-6AC1-11cf-8ADB-00AA00C00905

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Licenses\BC96F860-9928-11cf-8AFA-00AA00C00905

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Licenses\E32E2733-1BC5-11d0-B8C3-00A0C90DCA10

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Licenses\F4FC596D-DFFE-11CF-9551-00AA00A3DC45

It modifies the following registry entries to hide files with Hidden attributes:

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

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

File Infection

This worm propagates via shared networks and drops copies of itself into available networks.

Other Details

This worm connects to the following possibly malicious URL:

  • http://{BLOCKED}ts.web.rcn.net/cgi-bin/Count.cgi?df=765247

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 5.154.10
FIRST VSAPI PATTERN DATE: 12 Mar 2008
VSAPI OPR PATTERN File: 5.155.00
VSAPI OPR PATTERN Date: 12 Mar 2008

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Restart in Safe Mode

[ Learn More ]

Step 3

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\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • ScanRegistry = "scanregw.exe /scan"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Licenses
    • {default} = "Licensing: Copying the keys may be a violation of established copyrights."

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_LOCAL_MACHINE\SOFTWARE\Classes\Licenses
    • 096EFC40-6ABF-11cf-850C-08002B30345D
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Licenses
    • 096EFC40-6ABF-11cf-850C-08002B30345D
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Licenses
    • 190B7910-992A-11cf-8AFA-00AA00C00905
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Licenses
    • 2c49f800-c2dd-11cf-9ad6-0080c7e7b78d
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Licenses
    • 4250E830-6AC2-11cf-8ADB-00AA00C00905
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Licenses
    • 4D553650-6ABE-11cf-8ADB-00AA00C00905
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Licenses
    • 556C75F1-EFBC-11CF-B9F3-00A0247033C4
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Licenses
    • 57CBF9E0-6AA7-11cf-8ADB-00AA00C00905
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Licenses
    • 5f54e750-ce26-11cf-8e43-00a0c911005a
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Licenses
    • 6FB38640-6AC7-11cf-8ADB-00AA00C00905
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Licenses
    • 72E67120-5959-11cf-91F6-C2863C385E30
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Licenses
    • 78E1BDD1-9941-11cf-9756-00AA00C00908
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Licenses
    • 7C35CA30-D112-11cf-8E72-00A0C90F26F8
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Licenses
    • 899B3E80-6AC6-11cf-8ADB-00AA00C00905
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Licenses
    • 9E799BF1-8817-11cf-958F-0020AFC28C3B
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Licenses
    • B1EFCCF0-6AC1-11cf-8ADB-00AA00C00905
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Licenses
    • BC96F860-9928-11cf-8AFA-00AA00C00905
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Licenses
    • E32E2733-1BC5-11d0-B8C3-00A0C90DCA10
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Licenses
    • F4FC596D-DFFE-11CF-9551-00AA00A3DC45

Step 5

Restore this modified 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\Explorer\Advanced
    • From: ShowSuperHidden = "0"
      To: ShowSuperHidden =  "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: WebView = "0"
      To: WebView =  "1" 
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\CabinetState
    • From: FullPath = "1"
      To: FullPath =  " 0 " 

Step 6

Search and delete these files

[ Learn More ]
There may be some component 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%\{malware name}.zip
  • %System%\MSWINSCK.OCX

Step 7

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


Did this description help? Tell us how we did.