|ALIAS:||W32/NetSky.F@mm, I-Worm.NetSky.f, W32.Netsky.F@mm|
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:
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:
[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.