Name :	Worm:W32/NetSky.B
Category:	Malware
Type:	Worm
Platform:	W32

A standalone malicious program which uses computer or network resources to make complete copies of itself. May include code or other malware to damage both the system and the network.

Special Disinfection Tool

F-Secure provides a special disinfection utility to eliminate a NetSky.B worm infection. You can download this utility from our ftp site:


Disinfection instructions can be found here:


System administrators who are using F-Secure Policy Manager, can distribute the tool as a JAR package automatically to all workstations. System administrators can download the JAR version from:

Worm:W32/ NetSky.B (also known as Moodown.B) worm was found on 18th of February 2004. It is a minor variant of NetSky.A worm that appeared 2 days earlier.

The worm spreads itself in e-mails inside a ZIP archive or as an executable attachment. It also copies itself to shared folders of all available drives. This allows the worm to spread in P2P (peer-to-peer) and local networks.


Installation

When the worm's file is run, it first shows a fake error messagebox:



Then the worm copies itself to Windows directory with SERVICES.EXE name and creates a startup key for this file in System Registry:


where %windir% represents Windows directory. At the same time the worm also attempts to delete the following key values:


After that the worm starts looking for e-mail addresses. It scans files with the following extensions on all available drives (c:-z:) except CD-ROM drives:


If the worm finds a folder with the 'sharing' or 'share' name, it copies itself to that folder with the following names:



Propagation (E-mail)

When Internet connection is available, the worm starts to spread itself. It creates ZIP archives with its file in Windows directory. The names of these ZIP archives are the same as the names of worm's files inside. The worm can use the following names for its attachments:


The worm can use one or two extensions for its attachments. For the first extension the worm uses the following:


For the second extension the worm uses the following:


The worm spreads itself in e-mails as a ZIP attachment or as an attachment with one of the above shown names.

The subject of an infected e-mail can be one of the following:


The body text of an infected e-mail can be one of the following:


The worm's file is attached to the infected e-mail inside a ZIP archive or as an normal binary file. A recipient has to unpack the worm's attachment from a ZIP archive and to run it or to run an executable attachment to get infected.


Detection

Detection for this malware is available in the following FSAV update:

[FSAV_Database_Version]
Version=2004-02-18_02