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Discovered: June 27, 2003
Updated: February 13, 2007 12:02:59 PM
Also Known As: Trojan.Win32.Atendo [KAV], W32/Payfor@M [McAfee]
Type: Worm
Systems Affected: Windows

W32.Atendo@mm is a worm that replies to all the email messages it finds in the Microsoft Outlook Inbox of an infected computer. The worm also contains a destructive payload that deletes certain files from an infected computer.

Antivirus Protection Dates

  • Initial Rapid Release version June 27, 2003
  • Latest Rapid Release version August 08, 2016 revision 023
  • Initial Daily Certified version June 27, 2003
  • Latest Daily Certified version August 09, 2016 revision 001
  • Initial Weekly Certified release date June 28, 2003

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Writeup By: Robert X Wang

Discovered: June 27, 2003
Updated: February 13, 2007 12:02:59 PM
Also Known As: Trojan.Win32.Atendo [KAV], W32/Payfor@M [McAfee]
Type: Worm
Systems Affected: Windows

When W32.Atendo@mm is executed, it does the following:

  1. Attempts to create the following folder:


  2. Attempts to insert the following files into the C:\ARQUIV~1\NORTON~1 folder:
    • Nav32.exe (Payload module, detected as W32.Atendo@mm)
    • Nav-32.exe (Mailer module, detected as W32.Atendo@mm)
    • Payback.doc (A clean Word document. Manually delete this file.)
    • D.exe (A malicious executable program, detected as W32.Atendo@mm)

      Note: Due to a bug in the code, if the worm failed to create the C:\ARQUIV~1\NORTON~1 folder, it will not be able to insert the above files.

  3. Adds the following values:

    "NAV Agent-1"="C:\ARQUIV~1\NORTON~1\nav32.exe"
    "NAV Agent-2"="C:\ARQUIV~1\NORTON~1\nav-32.exe"

    to the registry keys:


  4. Copies itself as:
    • C:\Windows\System\Nav.exe
    • C:\ARQUIV~1\NORTON~1\Nav.exe

  5. Executes the following files:
    • D.exe
    • Nav32.exe

When Nav32.exe is executed, it does the following:
  1. Adds the following values:

    "NAV Agent-"="C:\ARQUIV~1\NORTON~1\NAV.EXE"

    to the registry key:


  2. Searches for the files on all the drives, except the removable drives. The worm may also delete the files whose name contains any of the following strings:
    • wpe
    • winp
    • wpto
    • wpnt
    • top
    • pst
    • dbx
    • doc
    • mdb
    • xls
    • exe

      If the filename contains "doc," the worm replaces the original file with C:\ARQUIV~1\NORTON~1\Payback.doc.

When Nav-32.exe is executed, the worm replies to all the email messages in the Microsoft Outlook Inbox. Then, it deletes the originals.
The email has the following characteristics:

Subject : %ComputerName%
Body : %UserName%


Subject : Cliente pé no saco
Body :
    E aí meu, vc não dá mais notícias, tá fugido hein!!!
    Lembra daquela conversa, vamos aplicar no Domingos, já que ele nos abandonou

    > Anibal,
    > nao atenda este cliente pois é um chato.
    > o domingos falou que vai cobrar os olhos da cara se for atender.
    > Tambem nao aguenta mais ele.
    > ele incomada mais que tropa de camelos conforme vc disse
    > sds
    > Sidnei

    >> Oi Sidnei,
    >> Se este pessoal ligar, meta a faca.
    >> nao aguento mais ver este pessoal.
    >> Amigao, um abraco
    >> Anibal
    Incoming mail is certified Virus Free.
    Checked by AVG anti-virus system (http://www.grilosoft.com).
    Version: 6.0.445 / Virus Database: 250 - Release Date: 25/01/03

    Outgoing mail is certified Virus Free.
    Checked by AVG anti-virus system (http://www.grilosoft.com).
    Version: 6.0.449 / Virus Database: 251 - Release Date: 25/01/03
When D.exe is executed, the worm copies C:\ARQUIV~1\NORTON~1\Nav.exe to all the folders it finds on all the drives, except the removable drives, as Atendimento.doc.exe.


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: Robert X Wang

Discovered: June 27, 2003
Updated: February 13, 2007 12:02:59 PM
Also Known As: Trojan.Win32.Atendo [KAV], W32/Payfor@M [McAfee]
Type: Worm
Systems Affected: Windows

The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

  1. Disable System Restore (Windows Me/XP).
  2. Update the virus definitions.
  3. Do one of the following:
    • Windows 95/98/Me: Restart the computer in Safe mode.
    • Windows NT/2000/XP: End the worm process.
  4. Run a full system scan and delete all the files detected as W32.Atendo@mm.
    Delete the file, C:\ARQUIV~1\NORTON~1\Payback.doc.
  5. Reverse the changes that the worm made to the registry.
For details on each of these steps, read the following instructions.

1. Disabling System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.

Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.

For instructions on how to turn off System Restore, read your Windows documentation, or one of the following articles:
For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article, "Antivirus Tools Cannot Clean Infected Files in the _Restore Folder ," Article ID: Q263455.

2. Updating the virus definitions
Symantec Security Response fully tests all the virus definitions for quality assurance before they are posted to our servers. There are two ways to obtain the most recent virus definitions:

  • Running LiveUpdate, which is the easiest way to obtain virus definitions: These virus definitions are posted to the LiveUpdate servers once each week (usually on Wednesdays), unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, refer to the Virus Definitions (LiveUpdate).
  • Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted on U.S. business days (Monday through Friday). You should download the definitions from the Symantec Security Response Web site and manually install them. To determine whether definitions for this threat are available by the Intelligent Updater, refer to the Virus Definitions (Intelligent Updater).

    The Intelligent Updater virus definitions are available: Read "How to update virus definition files using the Intelligent Updater" for detailed instructions.

3. Restarting the computer in Safe mode or ending the Worm process
    Windows 95/98/Me
    Restart the computer in Safe mode. All the Windows 32-bit operating systems, except for 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."

    Windows NT/2000/XP
    To end the Trojan process:
    1. Press Ctrl+Alt+Delete once.
    2. Click Task Manager.
    3. Click the Processes tab.
    4. Double-click the Image Name column header to alphabetically sort the processes.
    5. Scroll through the list and look for Nav.exe, Nav32.exe, Nav-32.exe, and D.exe.
    6. As you find each file, click it, and then click End Process.
    7. Exit the Task Manager.

4. Scanning for and deleting the infected files
  1. Start your Symantec antivirus program and make sure that it is configured to scan all the files.
  2. Run a full system scan.
  3. If any files are detected as infected with W32.Atendo@mm, click Delete.

5. Reversing the changes made to the registry

: Symantec strongly recommends that you back up the registry before making any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify the specified keys only. Read the document, "How to make a backup of the Windows registry," for instructions.
  1. Click Start, and then click Run. (The Run dialog box appears.)
  2. Type regedit

    Then click OK. (The Registry Editor opens.)

  3. Navigate to the key:


  4. In the right pane, delete the values:

    "NAV Agent-1"="C:\ARQUIV~1\NORTON~1\nav32.exe"
    "NAV Agent-2"="C:\ARQUIV~1\NORTON~1\nav-32.exe"

  5. Navigate to the key:


  6. In the right pane, delete the values:

    "NAV Agent-"="C:\ARQUIV~1\NORTON~1\NAV.EXE"
    "NAV Agent-1"="C:\ARQUIV~1\NORTON~1\nav32.exe"
    "NAV Agent-2"="C:\ARQUIV~1\NORTON~1\nav-32.exe"

  7. Exit the Registry Editor.

Writeup By: Robert X Wang