Threat Description



Aliases: Worm:W32/NetSky.V
Category: Malware
Type: Worm
Platform: W32


A standalone malicious program which uses computer or network resources to make complete copies of itself.


Automatic Disinfection

Allow F-Secure Anti-Virus to disinfect the relevant files.

For more general information on disinfection, please see Removal Instructions .

Network Disinfection

For general instructions on disinfecting a local network infection, please see Eliminating A Local Network Outbreak.

Technical Details

Worm:W32/Netsky.V does not send itself as an e-mail attachment but uses HTML-encoded emails which exploit a vulnerability known as Microsoft Internet Explorer XML Page Object Type Validation Vulnerability (MS03-040) to try and download and execute itself to a vulnerable host computer.

Netsky.V also performs a Denial-of-Service (DoS) attack against certain sites.

NetSky.V worm was discovered late night on April 14th, 2004. The binary code bears high resemblance to the latest NetSky variant, NetSky.U. Sharing up to approximately 86% of the code.

Some of the worm's text strings are scrambled.


The worm's file is a packed PE executable of length 19432 bytes. Upon execution, NetSky.V copies itself as EastAV.exe file to Windows folder and adds a startup key for this file into System Registry:

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

where %WinDir% represents Windows folder name.

Propagation (E-mail)

Netsky.V arrives in infected emails but does not use an attachment. It sends HTML emails which exploit vulnerability known as Microsoft Internet Explorer XML Page Object Type Validation Vulnerability (MS03-040) that downloads a HTML page to the host.

This HTML page then uses another vulnerbility, Internet Explorer Object Data Remote Execution (MS03-032), that attempts to download the binary part of the worm using command line ftp client, and executes it.

Further information about these vulnerabilities, including a fix, is available from Microsoft:


The email harvesting functionality is identical to the variant NetSky.U.

The messages will have any of the following format:

Subject: Mail Delivery Sytem failure Body: The processing of this message can take a few minutes...

Subject: Mail delivery failed Body: Converting message. Please wait...

Subject: Server Status failure Body: Please wait while loading failed message...

Subject: Gateway Status failure Body: Please wait while converting the message...


Netsky.V has a payload. It performs a DoS (Denial of Service) attack on the following websites from 22nd to 29th of April 2004:



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