1. Symantec/
  2. Security Response/
  3. W32.Feebs


Risk Level 2: Low

January 7, 2006
May 17, 2007 10:00:37 PM
Infection Length:
Systems Affected:
W32.Feebs is a detection for a family of mass-mailing worm that also spreads through file-sharing networks and lowers security settings on the compromised computer. The worm may also send confidential information to a remote attacker via FTP.

The worm variant arrives as an email attachment with an .HTA extension. Once the .HTA file is viewed, a malicious JavaScript then drops or downloads a copy of the worm executable.

When the .HTA file is viewed, a malicious JavaScript downloads a base-64 encoded file from one or more of the following locations:
  • [http://]blomor.t35.com/[REMOVED]/app.c
  • [http://]boblol.zoo.by/[REMOVED]/ol.txt
  • [http://]doln.1gb.ru/[REMOVED]/staff.txt
  • [http://]duuw.nm.ru/[REMOVED]/ol.txt
  • [http://]fr33.by.ru/[REMOVED]/ol.txt
  • [http://]poolcool.t35.com/[REMOVED]/bl.c
  • [http://]reep.wol.bz/[REMOVED]/ol.txt
  • [http://]roox.biz.ly/[REMOVED]/ol.txt
  • [http://]volum.1gb.ru/[REMOVED]/ol.txt
  • [http://]yorap.1gb.ru/[REMOVED]/hol.txt
  • [http://]ssddsf.coconia.net/[REMOVED]/lol.txt
  • [http://]pogc.wol.bz/[REMOVED]/lol.txt
  • [http://]jppo.t35.com/[REMOVED]/lol.c
  • [http://]jmo31.by.ru/[REMOVED]/big.txt

It then extracts a Windows executable file from the base-64 encoded file and saves it as C:\recycled\userinit.exe.

Once the W32.Feebs variant is executed, it create the following registry entries so that it runs every time Windows starts:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\ShellServiceObjectDelayLoad\"[FILE NAME OF DLL WORM COMPONENT]" = "{[RANDOM CLSID]}"

It then creates the following registry entries:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components\{CD5AC91B-AE7B-E83A-0C4C-E616075972F3}\"Stubpath" = "C:\Recycled\userinit.exe"
HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\"mal" = "[EMAIL ADDRESS OF RECIPIENT]"

The worm variant may send emails to all addresses found on the compromised computer. Following is an example of the email characterstics:

From: [STRING 1] [STRING 2]

Where [STRING 1] is one of the following:
  • protect
  • secur
  • security
  • securmail

and [STRING 2] is one of the following:
  • @hotmail.com
  • @gmail.com
  • @aol.com
  • @msn.com
  • @yahoo.com

Subject: [STRING 1] [STRING 2] [STRING 3]

Where [STRING 1] is one of the following:
  • Secure
  • Protected
  • Encrypted
  • Extended

[STRING 2] is one of the following:
  • Mail
  • E-Mail
  • Message
  • Html

[STRING 3] is one of the following:
  • [BLANK]
  • System
  • Service
  • Service ([DOMAIN])
  • from [DOMAIN] user.

[STRING 4] is one of the following:
  • Thank you
  • Sincerely
  • Best Regards

For example:
Protected Message from Gmail.com user.
Secure Mail Service (HotMail.com)
Encrypted E-mail from Yahoo.com user.

You have received [STRING 1] [STRING 2] from [DOMAIN] user.
This message is addressed personally for you.

To decrypt your message use the following details:

Keep your password in a safe place and under no circumstances give it to ANYONE.
[STRING 1] [STRING 2] and instruction is attached.


Where [STRING 1] is one of the following:
  • Secure
  • Protected
  • Encrypted
  • Extended

[STRING 2] is one of the following:
  • Mail
  • E-Mail
  • Message
  • Html

[STRING 3] is one of the following:
  • [BLANK]
  • System
  • Service
  • Service ([DOMAIN])
  • from [DOMAIN] user.

[STRING 4] is one of the following:
  • Thank you
  • Sincerely
  • Best Regards

For example:
You have received Encrypted Message from MSN.com user.
This message is addressed personally for you.

To decrypt your message use the following details:
ID: 44321
Password: mxsjstjgd

Keep your password in a safe place and under no circumstances give it to ANYONE.
Encrypted Message and instruction is attached.
Best Regards,
Encrypted E-mail Service,

One of the following:
  • msg.zip
  • message.zip
  • data.zip
  • mail.zip

The attachment contains a copy of the worm as an .hta file with the following name:


Where [STRING 1] is one of the following:
  • Secure
  • Protected
  • Encrypted
  • Extended

[STRING 2] is one of the following:
  • Mail
  • E-Mail
  • Message
  • Html

For example:
  • Extended Mail File.HTA
  • Extended E-Mail File.HTA
  • Secure Mail File.HTA
  • Secure E-Mail File.HTA

The worm varian may create the following files:
  • %System%\MS[RANDOM].exe
  • %System%\MS[RANDOM]
  • %System%\MS[RANDOM]32.DLL

The worm variant may load %System%\MS[RANDOM]32.DLL into all active processes and uses rootkit functionalities to hide its files and registry subkeys.

It also creates the following registry entry:
HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\"web"

The worm variant may create several registry subkeys containing configuration info, stolen passwords, accounts, and email addresses:

The worm variant then attempts to disable the Windows Firewall by modifying the following registry entries:
HKEY_CURRENT_USER\Software\Policies\Microsoft\WindowsFirewall\DomainProfile\"EnableFirewall" = "0"
HKEY_CURRENT_USER\Software\Policies\Microsoft\WindowsFirewall\StandardProfile\"EnableFirewall" = "0"
HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\WindowsFirewall\DomainProfile\"EnableFirewall" = "0"
HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\WindowsFirewall\StandardProfile\"EnableFirewall" = "0"

It may search for folders that contain the following strings:
  • downloads
  • share
  • incoming

The worm variant may copy itself to any folders that it finds as the following files:
  • 3dsmax_9_(3D_Studio_Max)_new!_full+crack.zip
  • ACDSee_9_new!_full+crack.zip
  • Adobe_Photoshop_10_(CS3)_new!_full+crack.zip
  • Adobe_Premiere_9_(2.0_pro)_new!_full+crack.zip
  • Ahead_Nero_8_new!_full+crack.zip
  • DivX_7.0_new!_full+crack.zip
  • ICQ_2006_new!_full+crack.zip
  • Internet_Explorer_7_new!_full+crack.zip
  • Kazaa_4_new!_full+crack.zip
  • Longhorn_new!_full+crack.zip
  • Microsoft_Office_2006_new!_full+crack.zip
  • winamp_5.2_new!_full+crack.zip

The .zip file contains a non-malicious text file that matches the name of the .zip file. It is reported that the text file's name does not include the string "_new!_full+crack".

It may delete all the startup registry subkeys associated with these services under the following subkey:

The worm variant may start a local Web server on TCP port 80. When a user connects to the Web server, it loads the .HTA file and also gives a link to offline.zip, which is a zip file containing the worm.

It may then gather sensitive information from the compromised computer by monitoring open windows. This includes monitoring for WebMoney, ICQ, and cryptography key files.

The worm variant may send this information to a remote attacker.

It may lower security settings on the compromised computer by ending security-related programs and by stopping services with names starting with one of the following strings:
  • armor2net
  • armorwall
  • avgcc
  • avp6
  • aws
  • bgnewsui
  • blackd
  • bullguard
  • ca
  • ccapp
  • ccevtmgr
  • ccproxy
  • ccsetmgr
  • dfw
  • dpf
  • fbtray
  • fireballdta
  • FirePM
  • firesvc
  • firewal
  • fsdfwd
  • fw
  • fwsrv
  • goldtach
  • hacker
  • hackereliminator
  • iamapp
  • iamserv
  • internet security
  • ipatrol
  • ipcserver
  • jammer
  • kaspe
  • kavpf
  • keylog
  • keypatrol
  • KmxAgent
  • KmxBiG
  • KmxCfg
  • KmxFile
  • KmxFw
  • KmxIds
  • KmxNdis
  • KmxSbx
  • kpf4gui
  • kpf4ss
  • leviathantrial
  • looknstop
  • mcafeefire
  • mpftray
  • netlimiter
  • npfc
  • npfmsg
  • npfsvice
  • npgui
  • opf
  • opfsvc
  • outpost
  • pavfnsvr
  • pccpfw
  • pcipim
  • pcIPPsC
  • persfw
  • rapapp
  • RapDrv
  • smc
  • sndsrvc
  • spfirewallsvc
  • spfw
  • sppfw
  • sspfwtry2
  • s-wall
  • symlcsvc
  • ton
  • tzpfw
  • umxtray
  • vipnet
  • vsmon
  • xeon
  • xfilter
  • zapro
  • zlclient
  • zonealarm


Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
  • Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
  • Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.
Writeup By: Kaoru Hayashi
Summary| Technical Details| Removal

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