Threat description




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.


Automatic action

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Technical Details

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.


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:

  • [HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run] "service" = "%windir%\services.exe -serv"

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

  • [HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run] "Taskmon" "Explorer" "system." "KasperskyAv"
  • [HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run] "Taskmon" "Explorer"
  • [HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices] "system."
  • [HKCR\CLSID\{E6FB5E20-DE35-11CF-9C87-00AA005127ED}\InProcServer32]

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:

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

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

  • winxp_crack.exe
  • dolly_buster.jpg.pif
  • strippoker.exe
  • photoshop 9 crack.exe
  • matrix.scr
  • porno.scr
  • angels.pif
  • hardcore porn.jpg.exe
  • office_crack.exe
  • serial.txt.exe
  • cool screensaver.scr
  • eminem - lick my pussy.mp3.pif
  • nero.7.exe
  • virii.scr
  • e-book.archive.doc.exe
  • max payne 2.crack.exe
  • how to hack.doc.exe
  • programming basics.doc.exe
  • e.book.doc.exe
  • win longhorn.doc.exe
  • dictionary.doc.exe
  • rfc compilation.doc.exe
  • sex sex sex sex.doc.exe
  • doom2.doc.pif
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:

  • document
  • msg
  • doc
  • talk
  • message
  • creditcard
  • details
  • attachment
  • me
  • stuff
  • posting
  • textfile
  • concert
  • information
  • note
  • bill
  • swimmingpool
  • product
  • topseller
  • ps
  • shower
  • aboutyou
  • nomoney
  • found
  • story
  • mails
  • website
  • friend
  • jokes
  • location
  • final
  • release
  • dinner
  • ranking
  • object
  • mail2
  • part2
  • disco
  • party
  • misc

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

  • .txt
  • .rtf
  • .doc
  • .htm

For the second extension the worm uses the following:

  • .exe
  • .scr
  • .com
  • .pif

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:

  • hi
  • hello
  • read it immediately
  • something for you
  • warning
  • information
  • stolen
  • fake
  • unknown

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

  • anything ok?
  • what does it mean?
  • ok
  • i'm waiting
  • read the details.
  • here is the document.
  • read it immediately!
  • my hero
  • here
  • is that true?
  • is that your name?
  • is that your account?
  • i wait for a reply!
  • is that from you?
  • you are a bad writer
  • I have your password!
  • something about you!
  • kill the writer of this document!
  • i hope it is not true!
  • your name is wrong
  • i found this document about you
  • yes, really?
  • that is bad
  • here it is
  • see you
  • greetings
  • stuff about you?
  • something is going wrong!
  • information about you
  • about me
  • from the chatter
  • here, the serials
  • here, the introduction
  • here, the cheats
  • that's funny
  • do you?
  • reply
  • take it easy
  • why?
  • thats wrong
  • misc
  • you earn money
  • you feel the same
  • you try to steal
  • you are bad
  • something is going wrong
  • something is fool

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.

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