F-Secure provides the special disinfection utility to eliminate
Netsky.Z worm infection. You can download this utility from our
ftp site:
ftp://ftp.f-secure.com/anti-virus/tools/f-netsky.exe
ftp://ftp.f-secure.com/anti-virus/tools/f-netsky.zip
Disinfection instructions can be found here:
ftp://ftp.f-secure.com/anti-virus/tools/f-netsky.txt
The worm's file is a PE executable 22016 bytes long packed with a
new or modified file compressor. Some of the worm's text strings
are encrypted.
Installation to system
Upon execution NetSky.Z copies itself as Jammer2nd.exe file to
Windows folder and adds a startup key for this file into System
Registry:
[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]
"Jammer2nd" = "%WinDir%\Jammer2nd.exe"
where %WinDir% represents Windows folder name.
Additionally the worm creates a few files with .LOG extension in
Windows folder. These files contain binary and MIME-encoded
copies of the worm's executable that will be sent in e-mails.
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:
.cfg
.mbx
.mdx
.pl
.htm
.html
.asp
.wab
.doc
.eml
.txt
.php
.vbs
.rtf
.uin
.shtm
.cgi
.dhtm
.ods
.stm
.xls
.adb
.tbb
.dbx
.mht
.mmf
.nch
.sht
.oft
.msg
.jsp
.wsh
.xml
.ppt
The worm spreads itself in e-mails It sends messages with
different subject lines, body text and attachment names. Here's
the list of subjects that the worm uses:
Important
Document
Hello
Information
Hi
The message body is composed from one the following strings:
Important details!
Important notice!
Important document!
Important bill!
Important data!
Important!
Important textfile!
Important informations!
The attachment name is selected from the following variants:
Details.zip
Notice.zip
Important.zip
Bill.zip
Data.zip
Part-2.zip
Textfile.zip
Informations.zip
The ZIP attachments contain worm's executables with one of the
following names:
Informations.txt <lots of spaces> .exe
Textfile.txt <lots of spaces> .exe
Part-2.txt <lots of spaces> .exe
Data.txt <lots of spaces> .exe
Bill.txt <lots of spaces> .exe
Important.txt <lots of spaces> .exe
Notice.txt <lots of spaces> .exe
Details.txt <lots of spaces> .exe
Backdoor
The worm has a backdoor that listens on TCP port 665. It allows
to download and execute files on an infected computer.
Payload
NetSky.Z has a payload. It performs a DoS (Denial of Service)
attack on the following websites from 2nd to 5th of May, 2004:
www.educa.ch
www.medinfo.ufl.edu
www.nibis.de
Detection of NetSky.Z worm was published on April 21st, 2004 in
the following F-Secure Anti-Virus updates:
[FSAV_Database_Version]
Version=2004-04-21_05
Technical Details:
Alexey Podrezov, April 21st, 2004;
Description Updated:
Alexey Podrezov, April 29th, 2004;
F-Secure Corporation
