Threat Description



Category: Malware
Type: Email-Worm
Platform: W32
Aliases: NetSky.G, W32/NetSky.G@mm, I-Worm.NetSky.g, W32.NetSky.G@mm


Another NetSky worm variant - NetSky.G was found on 4th of March 2004. This variant spreads itself in e-mails as an executable attachment.This worm contains another insulting message for the authors of Bagle and Mydoom worms and a proposal to meet in person in some location in the USA. The location name is encrypted.Like its previous variants NetSky.G tries to uninstall Bagle worm variants from an infected computer.


Automatic action

Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.

More scanning & removal options

More information on scanning or removal options is available in the documentation for your F-Secure security product on the Downloads section of our Home - Global site.

You may also refer to the Knowledge Base on the F-Secure Community site for further assistance.

Eliminating a Local Network Outbreak

If the infection is in a local network, please follow the instructions on this webpage:

Technical Details

Descriptions of all previous NetSky worm variants can be found here:

The worm's file is a PE executable file about 27 kilobytes long, packed with PE-Patch and TELock file compressors. The unpacked file's size is over 31 kilobytes.

On March 10th, 2004 the worm constantly beeps with PC speaker from 6:00 to 8:59. Below is the link to the WAV file with the sound that the worm makes:

NetSky.G worm doesn't copy its files to shared folders.

Installation to system

When run, the worm installs itself to system. It copies its file to Windows folder as AVGUARD.EXE and creates a startup key for this file in System Registry:

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]  "Special Firewall Service" = "%windir%\avguard.exe -av service"  

where %windir% represents Windows directory

The worm creates a mutex named "Netsky AV Guard" to avoid running more than one instance of itself.

Spreading in e-mails

NetSky.G worm has its own SMTP engine that it uses to send emails with infected attachments to all found e-mail addresses. The worm uses different subjects, message body texts and attachment names in its e-mails.

The worm scans all available drives except CD-ROM drives for e-mails. It searches for e-mail addresses in files with the following extensions:

.eml  .txt  .php  .pl  .htm  .html  .vbs  .rtf  .uin  .asp  .wab  .doc  .adb  .tbb  .dbx  .sht  .oft  .msg  .shtm  .cgi  .dhtm  

The subject for infected messages is selected from the following list:

Re: Document  Re: Re: Document  Re: Re: Thanks!  Re: Thanks!  Re: Your document  Re: Here is the document  Re: Your picture  Re: Re: Message  Re: Hi  Re: Hello  Re: Re: Re: Your document  Re: Here  Re: Your music  Re: Your software  Re: Approved  Re: Details  Re: Excel file  Re: Word file  Re: My details  Re: Your details  Re: Your bill  Re: Your text  Re: Your archive  Re: Your letter  Re: Your product  Re: Your website  

The message body text for infected messages is selected from the following list:

Your document is attached.  Here is the file.  See the attached file for details.  Please have a look at the attached file.  Please read the attached file.  Your file is attached.  

The attachment name for infected messages is selected from the following list:

your_document.pif  your_document.pif  document.pif  message_part2.pif  your_document.pif  document_full.pif  your_picture.pif  message_details.pif  your_file.pif  your_picture.pif  document_4351.pif  yours.pif  mp3music.pif  application.pif  all_document.pif  my_details.pif  document_excel.pif  document_word.pif  my_details.pif  your_details.pif  your_bill.pif  your_text.pif  your_archive.pif  your_letter.pif  your_product.pif  your_website.pif  

The worm avoids sending e-mails to e-mail addresses that contain any of the following substrings:

icrosoft  antivi  ymantec  spam  avp  f-secur  itdefender  orman  cafee  aspersky  f-pro  orton  fbi  abuse  messagelabs  skynet  andasoftwa  freeav  sophos  antivir  iruslis  
Deleting Registry keys and disinfecting Bagle worm

The NetSky.G worm variant of the worm deletes the following Registry keys:

[HKCR\CLSID\{E6FB5E20-DE35-11CF-9C87-00AA005127ED}\InProcServer32] [HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\PINF] [HKLM\System\CurrentControlSet\Services\WksPatch] [HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices]  system. [HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]  KasperskyAv  Explorer  Taskmon  system.  msgsvr32  DELETE ME  service  Sentry  Windows Services Host [HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]  KasperskyAv  Explorer  OLE  Windows Services Host  d3dupdate.exe  au.exe  sysmon.exe  rate.exe  gouday.exe  sate.exe  ssate.exe  srate.exe  

NetSky.G worm removes Registry keys of several Bagle worm variants if it finds them on an infected computer. At least the last 8 keys listed above belong to earlier Bagle variants.


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