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F-Secure Virus Descriptions : NetSky.G

[Summary] | [Disinfection] | [Detailed Description] | [Detection]

NAME:	NetSky.G
ALIAS:	W32/NetSky.G@mm, I-Worm.NetSky.g, W32.NetSky.G@mm

Summary

Another NetSky worm variant - NetSky.G was found on 4th of March 2004. This variant spreads itself in e-mails as an executable attachment.

This worm contains another insulting message for the authors of Bagle and Mydoom worms and a proposal to meet in person in some location in the USA. The location name is encrypted.

Like its previous variants NetSky.G tries to uninstall Bagle worm variants from an infected computer.

Disinfection

F-Secure provides the special disinfection utility to eliminate Netsky.G 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

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:

http://www.europe.f-secure.com/tools/f-netsky.jar

ftp://ftp.europe.f-secure.com/anti-virus/tools/f-netsky.jar

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Detailed Description

Descriptions of all previous NetSky worm variants can be found here:

W32/NetSky.A@mm: http://www.f-secure.com/v-descs/moodown.shtml

W32/NetSky.B@mm: http://www.f-secure.com/v-descs/netsky_b.shtml

W32/NetSky.C@mm: http://www.f-secure.com/v-descs/netsky_c.shtml

W32/NetSky.D@mm: http://www.f-secure.com/v-descs/netsky_d.shtml

W32/NetSky.E@mm: http://www.f-secure.com/v-descs/netsky_e.shtml

W32/NetSky.F@mm: http://www.f-secure.com/v-descs/netsky_f.shtml

The worm's file is a PE executable file about 27 kilobytes long, packed with PE-Patch and TELock file compressors. The unpacked file's size is over 31 kilobytes.

On March 10th, 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.G 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 AVGUARD.EXE and creates a startup key for this file in System Registry:

 [HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]
 "Special Firewall Service" = "%windir%\avguard.exe -av service"

where %windir% represents Windows directory.

The worm creates a mutex named "Netsky AV Guard" to avoid running more than one instance of itself.

Spreading in e-mails

NetSky.G 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:

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

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

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

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

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

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

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

NetSky.G worm removes Registry keys of several Bagle worm variants if it finds them on an infected computer. At least the last 8 keys listed above belong to earlier Bagle variants.

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Detection

Detection of NetSky.G worm is available in the following FSAV updates:

[FSAV_Database_Version]

Version=2004-03-04_02

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Technical Details: Alexey Podrezov, March 4th, 2004;

Description Updated: Alexey Podrezov, March 18th, 2004;

F-Secure Corporation