W32.Bugbear@mm is a mass-mailing worm. It can also spread through network shares. It has keystroke-logging and backdoor capabilities. The worm also attempts to terminate the processes of various antivirus and firewall programs.

It is written in the Microsoft Visual C++ 6 programming language and is compressed with UPX v0.76.1-1.22.

Wild:

• Number of infections: More than 1000
• Number of sites: More than 10
• Geographical distribution: High
• Threat containment: Moderate
• Removal: Moderate

Damage:

• Payload:
  
  • Large scale e-mailing: Attemps to mass-mail to addresses harvested from a compromised host using it's own SMTP engine
  • Compromises security settings: May allow unauthorized access to compromised machines. Attempts to terminate processes of various antivirus and firewall programs.

Distribution:

• Subject of email: Variable
• Name of attachment: Variable, with double extension ending in .exe, .scr, or .pif
• Size of attachment: 50,688 bytes
• Ports: 36794
• Shared drives: Attempts to connect to available network resources

When W32.Bugbear@mm runs, it does the following:

It copies itself as %system%\????.exe, where ? represents letters that are chosen by the worm.

NOTE: %system% is a variable. The worm locates the System folder and copies itself to that location. By default this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP

It copies itself to the \Startup folder as ???.exe, where ? represents letters that are chosen by the
worm. For example,

• It may copy itself as C:\Windows\Start Menu\Programs\Startup\Cuu.exe when it runs on a Windows 95/98/Me-based system
• It may copy itself as C:\Documents and Settings\<current user name>\Start Menu\Programs\Startup\Cti.exe when it runs on a Windows NT/2000/XP-based system.

It creates three encrypted .dll files in the %system% folder and two encrypted .dat files in the %windir% folder. One of the dropped .dll files is used by the worm to install hook procedures into a hook chain to monitor the system for any keyboard and mouse messages. The keyboard hook procedures process the messages and pass the hook information to the next hook procedure in the current hook chain. This allows the worm to intercept keystrokes. The installed .dll is 5,632 bytes in size and is detected by Symantec antivirus product as PWS.Hooker.Trojan.

Files that are not detected by Symantec antivirus product are not malicious. The worm uses them to store internal configuration information in an encrypted form. You should delete these files manually. For example, the worm may create the following files:

• %system%\Iccyoa.dll
• %system%\Lgguqaa.dll
• %system%\Roomuaa.dll
• %windir%\Okkqsa.dat
• %windir%\Ussiwa.dat

NOTES: %windir% is a variable. The worm locates the \Windows folder (by default this is C:\Windows or C:\Winnt) and creates files in that location.

It creates the following value

<random letters> <the worm's file name>

in the registry key

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnce

NOTE: Normally, the operating system removes values from this key as soon as the programs
refered to by these values are launched during startup. In this case the worm recreates the value so that it starts each time that you start Windows.

The worm creates four major threads. The first one activates its payload every 30 seconds to stop
the following processes if they are running:

• Zonealarm.exe
• Wfindv32.exe
• Webscanx.exe
• Vsstat.exe
• Vshwin32.exe
• Vsecomr.exe
• Vscan40.exe
• Vettray.exe
• Vet95.exe
• Tds2-Nt.exe
• Tds2-98.exe
• Tca.exe
• Tbscan.exe
• Sweep95.exe
• Sphinx.exe
• Smc.exe
• Serv95.exe
• Scrscan.exe
• Scanpm.exe
• Scan95.exe
• Scan32.exe
• Safeweb.exe
• Rescue.exe
• Rav7win.exe
• Rav7.exe
• Persfw.exe
• Pcfwallicon.exe
• Pccwin98.exe
• Pavw.exe
• Pavsched.exe
• Pavcl.exe
• Padmin.exe
• Outpost.exe
• Nvc95.exe
• Nupgrade.exe
• Normist.exe
• Nmain.exe
• Nisum.exe
• Navwnt.exe
• Navw32.exe
• Navnt.exe
• Navlu32.exe
• Navapw32.exe
• N32scanw.exe
• Mpftray.exe
• Moolive.exe
• Luall.exe
• Lookout.exe
• Lockdown2000.exe
• Jedi.exe
• Iomon98.exe
• Iface.exe
• Icsuppnt.exe
• Icsupp95.exe
• Icmon.exe
• Icloadnt.exe
• Icload95.exe
• Ibmavsp.exe
• Ibmasn.exe
• Iamserv.exe
• Iamapp.exe
• Frw.exe
• Fprot.exe
• Fp-Win.exe
• Findviru.exe
• F-Stopw.exe
• F-Prot95.exe
• F-Prot.exe
• F-Agnt95.exe
• Espwatch.exe
• Esafe.exe
• Ecengine.exe
• Dvp95_0.exe
• Dvp95.exe
• Cleaner3.exe
• Cleaner.exe
• Claw95cf.exe
• Claw95.exe
• Cfinet32.exe
• Cfinet.exe
• Cfiaudit.exe
• Cfiadmin.exe
• Blackice.exe
• Blackd.exe
• Avwupd32.exe
• Avwin95.exe
• Avsched32.exe
• Avpupd.exe
• Avptc32.exe
• Avpm.exe
• Avpdos32.exe
• Avpcc.exe
• Avp32.exe
• Avp.exe
• Avnt.exe
• Avkserv.exe
• Avgctrl.exe
• Ave32.exe
• Avconsol.exe
• Autodown.exe
• Apvxdwin.exe
• Anti-Trojan.exe
• Ackwin32.exe
• _Avpm.exe
• _Avpcc.exe
• _Avp32.exe

The worm determines which version of the operating system is running and uses different routines to accomplish its task.

The second thread is responsible for the mass-mailing payload. It searches for email addresses in
the current inbox and in files that have these extensions:

• .mmf
• .nch
• .mbx
• .eml
• .tbb
• .dbx
• .ocs

It retrieves the current user's email address and SMTP server from the registry key

HKEY_CURRENT_USER\SOFTWARE\Microsoft\Internet Account Manager\Accounts

It then uses its own SMTP engine to send itself to all email addresses that it finds. The email
message may have one of the following subjects:

• Greets!
• Get 8 FREE issues - no risk!
• Hi!
• Your News Alert
• $150 FREE Bonus!
• Re:
• Your Gift
• New bonus in your cash account
• Tools For Your Online Business
• Daily Email Reminder
• News
• free shipping!
• its easy
• Warning!
• SCAM alert!!!
• Sponsors needed
• new reading
• CALL FOR INFORMATION!
• 25 merchants and rising
• Cows
• My eBay ads
• empty account
• Market Update Report
• click on this!
• fantastic
• wow!
• bad news
• Lost & Found
• New Contests
• Today Only
• Get a FREE gift!
• Membership Confirmation
• Report
• Please Help...
• Stats
• I need help about script!!!
• Interesting...
• Introduction
• various
• Announcement
• history screen
• Correction of errors
• Just a reminder
• Payment notices
• hmm..
• update
• Hello!
  

SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders

and lists the files that are stored at that location (which by default is C:\My Documents on Windows 95/98/Me and C:\Documents and Settings\<User Name>\My Documents on Windows NT/2000/XP). These retrieved file names may be used to compose file name of the viral attachment. In addition, the file name may consist of one of the following words:

• readme
• Setup
• Card
• Docs
• news
• image
• images
• pics
• resume
• photo
• video
• music
• song
• data

The file name's extension is chosen from the following list:

• .scr
• .pif
• .exe

If the worm used a file name that it retrieved from the My Documents folder, it will modify the content type of the message to match the file's extension. The list of the analysed extensions is:

• .reg
• .ini
• .bat
• .diz
• .txt
• .cpp
• .html
• .htm
• .jpeg
• .jpg
• .gif
• .cpl
• .dll
• .vxd
• .sys
• .com
• .exe
• .bmp

The content type of the composed message is modified to one of the following:

• text/html
• text/plain
• application/octet-stream
• image/jpeg
• image/gif

The email message can be composed with or without the use of the Incorrect MIME Header Can
Cause IE to Execute E-mail Attachment vulnerability to autoexecute on a vulnerable system.

The third thread that the worm creates is a backdoor routine. It opens port 36794 and listens for commands from the hacker. The commands permit the worm to perform the following actions:

• Delete files.
• Terminate processes.
• List processes and deliver the list to the hacker.
• Copy files.
• Start processes.
• List files and deliver the list to the hacker.
• Deliver intercepted keystrokes to the hacker (in an encrypted form). This may release confidential information that typed on a computer (passwords, login details, and so on).
• Deliver the system information to the hacker in the following form:
  • User: <user name>
  • Processor: <type of processor used>
  • Windows version: <Windows version, build number>
  • Memory information: <Memory available, etc.>
  • Local drives, their types (e.g., fixed/removable/RAM disk/CD-ROM/remote), and their
    physical characteristics
• List network resourses and their types, and deliver the list to the hacker.

If the operating system is Windows 95/98/Me, the worm attempts to obtain access to the password cache on the local computer. The cached passwords include modem and dial-up passwords, URL passwords, share passwords, and others. This is done using an officially undocumented function--WNetEnumCachedPasswords--that exists only in Windows95/98/Me versions of the Mpr.dll file.

One of the commands permits the Trojan component to deliver data using HTTP port 80. The results of the backdoor activity may be represented in the form of HTML pages. This gives a hacker a convienient way to browse the compromised computer resources.

The fourth worm thread replicates across the network. To do this, the worm lists all of the resources in the network. If it locates open administrator shares, it attempts to copy itself to the Startup folder of the remote computer. This leads to the infection of the compromised network computers as soon as they are restarted.

Because the worm does not properly handle the network resource types, it may flood shared printer resources, which causes them to print garbage or disrupt their normal functionality.

Recommendations

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

• Turn off and remove unneeded services. By default, many operating systems install auxiliary services that are not critical, such as an FTP server, telnet, and a Web server. These services are avenues of attack. If they are removed, blended threats have less avenues of attack and you have fewer services to maintain through patch updates.
• If a blended 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.
• 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.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread viruses, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate infected computers quickly to prevent further compromising your organization. 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.

Removal

1. Update the virus definitions.
2. Restart the computer in Safe mode.
3. Run a full system scan, and delete all files that are detected as W32.Bugbear@mm.
4. Delete the value added by the worm from the registry key

   HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnce

For details on how to do this, read the following instructions.

To update the virus definitions:

NOTE: If the worm is currently active on your computer, you will not be able to run LiveUpdate. In this case, you must download the definitions using the Intelligent Updater.

All virus definitions receive full quality assurance testing by Symantec Security Response before
being posted to our servers. There are two ways to obtain the most recent virus definitions:

• Run LiveUpdate, which is the easiest way to obtain virus definitions. These virus definitions are posted to the LiveUpdate servers one time each week (usually Wednesdays) unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, look at the Virus Definitions (LiveUpdate) line at the top of this write-up.
• Download the definitions using the Intelligent Updater. Intelligent Updater virus definitions are posted on U.S. business days (Monday through Friday). They must be downloaded from the Symantec Security Response Web site and installed manually. To determine whether definitions for this threat are available by the Intelligent Updater, look at the Virus Definitions (Intelligent Updater) line at the top of this write-up.
  
  Intelligent Updater virus definitions are available here. For detailed instructions on how to download and install the Intelligent Updater virus definitions from the Symantec Security Response Web site, click here.

To restart the computer in Safe mode:
All Windows 32-bit operating systems, except Windows NT, can be restarted in Safe mode. For instructions on how to do this, read the document How to start the computer in Safe Mode.

To scan for and delete the infected files:

1. Start your Symantec antivirus program, and make sure that it is configured to scan all files.
• Norton AntiVirus consumer products: Read the document How to configure Norton AntiVirus to scan all files.
• Symantec enterprise antivirus products: Read the document How to verify a Symantec Corporate antivirus product is set to scan All Files.
2. Run a full system scan.
3. If any files are detected as infected with W32.Bugbear@mm, write down the file name and
then click Delete.

1. Click Start, and click Run. The Run dialog box appears.
2. Type regedit and then click OK. The Registry Editor opens.
3. Navigate to this key:

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnce

4. In the right pane, locate and delete the line that refers to the file that was detected as infected with W32.Bugbear@mm.
5. Exit the Registry Editor.