Threat Description

NetSky.X

Details

Aliases: NetSky.X, W32/NetSky.X@mm, I-Worm.Netsky.y
Category: Malware
Type: Email-Worm
Platform: W32

Summary


NetSky.X worm was discovered on April 20th, 2004.This variant is extremely close to the latest NetSky variants. It shares up to approximately 86% of the code and features in common with NetSky.U.



Removal


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


Netsky.X sends messages in several different languages: English, Swedish, Finnish, Polish, Norwegian, Portuguese, Italian, French, German and possibly the language of some small island called Turks and Caicos, located in the Atlantic ocean. In many cases the messages are composed incorrectly suggesting that the worm's author did not ask native speakers for translation or used an on-line translation service like Babel Fish.

Update on April 23rd, 2004

It looks like the Netsky's author mistyped the domain suffix for Turkey - he put '.tc' instead of '.tr'. We came to that conclusion after verifying that the text that is sent to addresses in .tc domain is in Turkish (word by word translation from dictionary).

The worm's file is a PE executable 26112 bytes long packed with PE-Patch and TeLock file compressors.

Some of the worm's text strings are scrambled using the same algorithm as all the other variants.

Installation to system

Upon execution NetSky.X copies itself as FirewalSrv.exe file to Windows folder and adds a startup key for this file into System Registry:

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]  "FirewallSvr" = "%WinDir%\FirewallSvr.exe"  

where %WinDir% represents Windows folder name.

Spreading in e-mail

Before spreading in e-mail the worm collects e-mail addresses. It scans all files on all drives from C: to Z: except CD-ROM drives. If any file with the following extensions is found, the worm opens it and searches for e-mail addresses there:

.eml  .txt  .php  .cfg  .mbx  .mdx  .asp  .wab  .doc  .vbs  .rtf  .uin  .shtm  .cgi  .dhtm  .adb  .tbb  .dbx  .pl  .htm  .html  .sht  .oft  .msg  .ods  .stm  .xls  .jsp  .wsh  .xml  .mht  .mmf  .nch  .ppt  

The worm composes two different types of messages. According to whether the destination address is one of the following domains:

.tc  .se  .fi  .pl  .no  .pt  .it  .fr  .de  .xx  

It will compose messages in the corresponding language, choosing from the following parts.

Subjects chosen from:

Re: belge  Re: dokumenten  Re: dokumentoida  Re: udokumentowac  Re: dokumentet  Re: original  Re: documento  Re: dokument  Re: document  

Bodies chosen from:

mutlu etmek okumak belgili tanimlik belge.  Behaga lasa dokumenten.  Haluta kuulua dokumentoida.  Podobac sie przeczytac ten udokumentowac.  Behage lese dokumentet.  Leia por favor o original.  Legga prego il documento.  Veuillez lire le document.  Bitte lesen Sie das Dokument.  Please read the document.  

Attachment filename:

belge.pif  dokumenten.pif  dokumentoida.pif  udokumentowac.pif  dokumentet.pif  original.pif  documento.pif  dokument.pif  document.pif  
Payload

Netsky.X has a payload. It performs a DoS (Denial of Service) attack on the following websites from 28th to 30rd of April 2004:

www.nibis.de  www.medinfo.ufl.edu  www.educa.ch  





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