1. Symantec/
  2. Security Response/
  3. W32.Swen.A@mm


Risk Level 2: Low

September 18, 2003
February 13, 2007 12:07:33 PM
Also Known As:
Swen [F-Secure], W32/Swen@mm [McAfee], W32/Gibe-F [Sophos], I-Worm.Swen [KAV], Win32 Swen.A [CA], WORM_SWEN.A [Trend], Worm.Automat.AHB [Previous Sym
Systems Affected:
CVE References:

When W32.Swen.A@mm is executed, it performs the following actions:
  1. Checks to see whether it has already been installed on the computer. If so, the installation procedure will end and display the following message:

  2. If the executed filename starts with the letter q, u, p, or i, the worm will present the user with the following dialog box:

    The worm will install itself regardless of the choice that is made. If you click No, the worm will be installed silently. If you click Yes, the following dialog boxes will be displayed while the worm is installed:

  3. Attempts to end the following processes:
    • _avp
    • Azonealarm
    • avwupd32
    • avwin95
    • avsched32
    • avp
    • avnt
    • avkserv
    • avgw
    • avgctrl
    • avgcc32
    • ave32
    • avconsol
    • autodown
    • apvxdwin
    • aplica32
    • anti-trojan
    • ackwin32
    • bootwarn
    • blackice
    • blackd
    • claw95
    • cfinet
    • cfind
    • cfiaudit
    • cfiadmin
    • ccshtdwn
    • ccapp
    • dv95
    • espwatch
    • esafe
    • efinet32
    • ecengine
    • f-stopw
    • frw
    • fp-win
    • f-prot95
    • fprot95
    • f-prot
    • fprot
    • findviru
    • f-agnt95
    • gibe
    • iomon98
    • iface
    • icsupp
    • icssuppnt
    • icmoon
    • icmon
    • icloadnt
    • icload95
    • ibmavsp
    • ibmasn
    • iamserv
    • iamapp
    • jedi
    • kpfw32
    • luall
    • lookout
    • lockdown2000
    • msconfig
    • mpftray
    • moolive
    • nvc95
    • nupgrade
    • nupdate
    • normist
    • nmain
    • nisum
    • navw
    • navsched
    • navnt
    • navlu32
    • navapw32
    • nai_vs_stat
    • outpost
    • pview
    • pop3trap
    • persfw
    • pcfwallicon
    • pccwin98
    • pccmain
    • pcciomon
    • pavw
    • pavsched
    • pavcl
    • padmin
    • rescue
    • regedit
    • rav
    • sweep
    • sphinx
    • serv95
    • safeweb
    • tds2
    • tca
    • vsstat
    • vshwin32
    • vsecomr
    • vscan
    • vettray
    • vet98
    • vet95
    • vet32
    • vcontrol
    • vcleaner
    • wfindv32
    • webtrap
    • zapro

  4. Drops a copy of itself to %Windir% with a randomly generated filename.

    Note: %Windir% is a variable. The worm locates the Windows installation folder (by default, this is C:\Windows or C:\Winnt) and copies itself to that location.

  5. Searches the .html, .asp, .eml, .dbx, .wab, and .mbx files on the hard disk for email addresses.

  6. Creates the file, %Windir%\Germs0.dbv, where it stores the email addresses it has found.

  7. Creates the file, %Windir%\Swen1.dat, where it stores a list of remote news and mail servers.

  8. Drops a %ComputerName%.bat file, which executes the worm and a randomly named configuration file to store the local, machine-specific data.

    Note: %ComputerName% is a variable that represents the name of the infected computer.

  9. Adds the values:
    • "CacheBox Outfit"="yes"
    • "ZipName"="<random>"
    • "Email Address"="<The current users email address that the worm retrieves from the registry>"
    • "Server"="<The IP address of the SMTP server that the worm retrieves from the registry>"
    • "Mirc Install Folder"="<location of mirc client on system>"
    • "Installed"="...by Begbie"
    • "Install Item"="<random>"
    • "Unfile"="<random>"

      to the key:


      where * is a random set of letters.

  10. Adds a randomly named value to:


    so that the worm starts when Windows starts.

  11. Modifies the following registry keys:
    • HKEY_LOCAL_MACHINE\Software\CLASSES\exefile\shell\open\command
    • HKEY_LOCAL_MACHINE\Software\CLASSES\regfile\shell\open\command
    • HKEY_LOCAL_MACHINE\Software\CLASSES\scrfile\shell\open\command
    • HKEY_LOCAL_MACHINE\Software\CLASSES\comfile\shell\open\command
    • HKEY_LOCAL_MACHINE\Software\CLASSES\batfile\shell\open\command
    • HKEY_LOCAL_MACHINE\Software\CLASSES\piffile\shell\open\command

      which hooks the worm to each of these file types.

  12. Modifies the value:

    "DisableRegistryTools" = "1"

    in the registry key:


    to prevent you from running Regedit on the computer.

  13. Periodically presents you with a fake MAPI32 Exception error:

    prompting you to enter the details of your email account, including the following:
    • Email address
    • Username
    • Password
    • POP3 server
    • SMTP server

  14. Using the username and password, the worm will log into the POP3 server and check your email. If the worm finds an email that the worm sent, it will be deleted. The worm will only delete the messages, which the currently infected computer has sent.

  15. Intercepts the execution of any of the processes listed in step three, preventing them from loading, and then displays the following fake error message:

  16. Sends an HTTP Get request to a predefined HTTP server to retrieve counter information when the worm runs for the first time. Then, the worm may display the counter information.

    For example:

  17. Attempts to create one or more compressed copies of itself using the Winzip file-compression utility, and then the Winrar file-compression utility.

    The worm spreads through email, KaZaA, IRC, mapped drives, and newsgroups. The following sections discuss how each of these transmission methods can occur.
Transmission through email
W32.Swen.A@mm sends a copy of itself to the addresses found on the system through various methods. The worm can vary the message it sends, as well as the filename that it attaches itself as. The worm may use an incorrect MIME Header exploit, mentioned in Microsoft Security Bulletin MS01-020, to ensure that it is automatically executed when the mail is viewed.

One of the messages, as shown here, pretends to be a critical message from Microsoft, suggesting that you update your system with the attached file.

Other messages can be constructes as follows:

The subject of the email can take one of two formats:

Subject 1

In this subject, the email contains up to four strings and may appear as lowercase:
  1. String 1
    • Current
    • Newest
    • Last
    • New
    • Latest
    • <empty>

  2. String 2
    • Net
    • Network
    • Microsoft
    • Internet
    • <empty>

  3. String 3
    • Critical
    • Security
    • <empty>

  4. String 4
    • Patch
    • Update
    • Pack
    • Upgrade

Subject 2
  1. String 1
    • RE:
    • FWD:
    • FW:
    • <empty>

  2. String 2
    • Check
    • Checkout
    • Prove
    • Taste
    • Try
    • TryOn
    • LookAt
    • TakeALookAt
    • See
    • Watch
    • Use
    • Apply
    • Install
    • <empty>

  3. String 3
    • this
    • that
    • the
    • these
    • <empty>

  4. String 4
    • important
    • internet
    • critical
    • security
    • corrective
    • correction
    • <empty>

  5. String 5
    • pack
    • package
    • patch
    • update
    • The subject for subject 2 may end here

  6. String 6
    • for
    • <emtpy>

  7. String 7
    • Windows
    • Internet Explorer
    • <empty if String 6 is empty>
    • The subject may end here

  8. String 8
    • which
    • that
    • <empty>

  9. String 9
    • came
    • comes
    • <empty if String 8 is empty>

  10. String 10
    • from

  11. String 11
    • the
    • <empty>

  12. String 12
    • MS
    • Microsoft
    • M$

  13. String 13
    • Corporation
    • Corp.
    • <empty>

The attachment name is created by:
  1. Selecting one of the following predetermined names:
    • Patch
    • Upgrade
    • Update
    • Installer
    • Install
    • Pack
    • Q

  2. Followed by a series of random numbers.

  3. And a file extension that is either .exe or .zip.

The worm can also impersonate mail delivery failure notices, attaching itself as a randomly named executable.

One example is:

I'm sorry I wasn't able to deliver your message to one or more destinations.

Transmission through KaZaA
When attempting to spread through KaZaA, W32.Swen.A@mm performs the following actions:
  1. Drops a .zip or .rar copy of itself into a randomly named subdirectory of %Temp% on the computer.

    Note: %Temp% is a variable. The worm locates the Windows installation folder (by default, this is C:\Windows or C:\Winnt) and copies itself to that location.

  2. Adds the values:

    "Dir99"= "012345:<random folder name>"

    to the registry key:


    which adds this folder to the list of shared folders in KaZaA.

    Note: <random folder name> is the folder created under %Temp% in step 1 above.

  3. Some of the possible dropped filenames include:
    • Virus Generator
    • Magic Mushrooms Growing
    • Cooking with Cannabis
    • Hallucinogenic Screensaver
    • My naked sister
    • XXX Pictures
    • Sick Joke
    • XXX Video
    • XP update
    • Emulator PS2
    • XboX Emulator
    • Sex
    • HardPorn
    • Jenna Jameson
    • 10.000 Serials
    • Hotmail hacker
    • Yahoo hacker
    • AOL hacker
    • fixtool
    • cleaner
    • removal tool
    • remover
    • Klez
    • Sobig
    • Sircam
    • Gibe
    • Yaha
    • Bugbear
    • installer
    • upload
    • warez
    • hacked
    • hack
    • key generator
    • Windows Media Player
    • GetRight FTP
    • Download Accelerator
    • Mirc
    • Winamp
    • WinZip
    • WinRar
    • KaZaA
    • KaZaA media desktop
    • Kazaa Lite

Transmission through IRC
When attempting to spread through IRC, W32.Swen.A@mm performs the following actions:
  1. Searches for a \Mirc folder.

  2. Creates a Script.ini file in this folder, which the worm uses to send .zip, .rar, or .exe files of itself to other mIRC users, who are connected on the same channel as the infected computer.

Transmission through mapped drives
When attempting to spread through mapped drives, W32.Swen.A@mm does so to the following locations:
    • \Win98\Start menu\Programs\Startup
    • \Win95\Start menu\Programs\Startup
    • \WinMe\Start menu\Programs\Startup
    • \Windows\Start menu\Programs\Startup
    • \Documents and Settings\All Users\Start menu\Programs\Startup
    • \Documents and Settings\Administrator\Start menu\Programs\Startup
    • \Documents and Settings\Default User\Start menu\Programs\Startup
    • \Winnt\Profiles\All Users\Start menu\Programs\Startup
    • \Winnt\Profiles\Administrator\Start menu\Programs\Startup
    • \Winnt\Profiles\Default User\Start menu\Programs\Startup
Transmission through newsgroups
The worm will enumerate the registry looking for newsgroup server addresses, and then attempt to contact that newsgroup server. If a newsgroup server is not configured on the system, the worm will randomly select one from a predefined list. The worm will download the available groups and post messages to randomly selected groups. The messages posted to the newsgroups are generated according to the same routine used for sending email.


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: John Canavan
Summary| Technical Details| Removal

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