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NetSky.F


Aliases:


NetSky.F
W32/NetSky.F@mm, I-Worm.NetSky.f, W32.Netsky.F@mm

Malware
Email-Worm
W32

Summary

NetSky.F worm variant was found on 3rd of March 2004. This variant spreads itself in e-mails as an executable attachment.



Disinfection & Removal


Automatic Disinfection

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

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


Eliminating a Local Network Outbreak

If the infection is in a local network, please follow the instructions on this webpage:



Technical Details

The following text string is present in the worm's body:

Skynet AntiVirus -  Bagle - you are a looser!!!!

This indicates an on-going competition/war among virus writers of the currently widespread malware: Bagle and NetSky. This NetSky worm variant tries to remove Bagle worm infection if it finds it on an infected computer.

Descriptions of all previous NetSky variants can be found here:

The worm's file is a PE executable file 18432 bytes long, packed with PE-Pack file compressor. The unpacked file's size is over 28 kilobytes.

On March 2nd, 2004 the worm constantly beeps with PC speaker from 6:00 to 8:59. Below is the link to the WAV file with the sound that the worm makes: http://www.f-secure.com/virus-info/v-pics/netsky_d.wav

NetSky.F worm doesn't copy its files to shared folders.


Installation to system

When run, the worm installs itself to system. It copies its file to Windows folder as SVCHOST.EXE and creates a startup key for this file in System Registry:

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]
 "Zone Labs Client Ex" = "%windir%\svchost.exe -antivirus service"

where %windir% represents Windows directory

The worm creates a mutex named "LK[SkyNet.cz]SystemsMutex" to avoid running more than one instance of itself.


Spreading in e-mails

NetSky.F worm has its own SMTP engine that it uses to send emails with infected attachments to all found e-mail addresses. The worm uses different subjects, message body texts and attachment names in its e-mails.

The worm scans all available drives except CD-ROM drives for e-mails. It searches for e-mail addresses in files with the following extensions:

.dhtm
 .cgi
 .shtm
 .msg
 .oft
 .sht
 .dbx
 .tbb
 .adb
 .doc
 .wab
 .asp
 .uin
 .rtf
 .vbs
 .html
 .htm
 .php
 .txt
 .eml

The subject for infected messages is selected from the following list:

Re: Your website
 Re: Your product
 Re: Your letter
 Re: Your archive
 Re: Your text
 Re: Your bill
 Re: Your details
 Re: My details
 Re: Word file
 Re: Excel file
 Re: Details
 Re: Approved
 Re: Your software
 Re: Your music
 Re: Here
 Re: Re: Re: Your document
 Re: Hello
 Re: Hi
 Re: Re: Message
 Re: Your picture
 Re: Here is the document
 Re: Your document
 Re: Thanks!
 Re: Re: Thanks!
 Re: Re: Document
 Re: Document

The message body text for infected messages is selected from the following list:

Your file is attached.
 Please read the attached file.
 Please have a look at the attached file.
 See the attached file for details.
 Here is the file.
 Your document is attached.

The attachment name for infected messages is selected from the following list:

your_website.pif
 your_product.pif
 your_letter.pif
 your_archive.pif
 your_text.pif
 your_bill.pif
 your_details.pif
 document_word.pif
 document_excel.pif
 my_details.pif
 all_document.pif
 application.pif
 mp3music.pif
 yours.pif
 document_4351.pif
 your_file.pif
 message_details.pif
 your_picture.pif
 document_full.pif
 message_part2.pif
 document.pif
 your_document.pif

The worm avoids sending e-mails to e-mail addresses that contain any of the following substrings:

icrosoft
 antivi
 ymantec
 spam
 avp
 f-secur
 itdefender
 orman
 cafee
 aspersky
 f-pro
 orton
 fbi
 abuse
 messagelabs
 skynet
 andasoftwa
 freeav
 sophos
 antivir
 iruslis


Deleting Registry keys and disinfecting Bagle worm

The NetSky.F worm variant of the worm deletes the following Registry keys:

[HKCR\CLSID\{E6FB5E20-DE35-11CF-9C87-00AA005127ED}\InProcServer32]
[HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\PINF]
[HKLM\System\CurrentControlSet\Services\WksPatch]
[HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices]
 system.
[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]
 KasperskyAv
 Explorer
 Taskmon
 system.
 msgsvr32
 DELETE ME
 service
 Sentry
 Windows Services Host
[HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]
 KasperskyAv
 Explorer
 OLE
 Windows Services Host
 d3dupdate.exe
 au.exe
 sysmon.exe
 rate.exe
 gouday.exe

NetSky.F worm removes Registry keys of several Bagle worm variants if it finds them on an infected computer. The last 5 keys listed above belong to earlier Bagle variants.







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