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_CLASSES_ROOT\CLSID\{[RANDOM CLSID]}\InprocServer32\"(default)" = "%System\[PATH TO DLL WORM COMPONENT]"
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:
[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.
Message: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:
ID: [RANDOM NUMBERS]
Password: [RANDOM LETTERS]
Keep your password in a safe place and under no circumstances give it to ANYONE.
[STRING 1] [STRING 2] and instruction is attached.
[STRING 4]
[STRING 1] [STRING 2] [STRING 3],
[DOMAIN]
Where [STRING 1] is one of the following:
- Secure
- Protected
- Encrypted
- Extended
[STRING 2] is one of the following:
[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,
MSN.com
Attachment:
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:
[STRING 1] [STRING 2] File.HTA
Where [STRING 1] is one of the following:
- Secure
- Protected
- Encrypted
- Extended
[STRING 2] is one of the following:
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:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MS[RANDOM 2 LETTERS]\dat
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MS[RANDOM 2 LETTERS]\cdat
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MS[RANDOM 2 LETTERS]\fdat
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MS[RANDOM 2 LETTERS]\rdat
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MS[RANDOM 2 LETTERS]\sdat
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MS[RANDOM 2 LETTERS]\ldat
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MS[RANDOM 2 LETTERS]\gdat
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MS[RANDOM 2 LETTERS]\pdat
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MS[RANDOM 2 LETTERS]\udat
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MS[RANDOM 2 LETTERS]\idat
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MS[RANDOM 2 LETTERS]\ddat
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MS[RANDOM 2 LETTERS]\kdat
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:
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:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\[SERVICE NAME]
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":
