Malware type: Worm

Aliases: Backdoor.Win32.Agobot.kb (Kaspersky), W32/Gaobot.worm.gen.t (McAfee), W32.Spybot.Worm (Symantec), Worm/AgoBot.KB.7 (Avira),

In the wild: No

Destructive: No

Language: English

Platform: Windows NT, 2000, XP

Encrypted: No

Overall risk rating:

Reported infections:

Damage potential:


Distribution potential:



This memory-resident worm exploits certain vulnerabilities to propagate across networks. Like the earlier AGOBOT variants, it takes advantage of the following Windows vulnerabilities:

  • Remote Procedure Call (RPC) Distributed Component Object Model (DCOM) vulnerability
  • IIS5/WEBDAV Buffer Overflow vulnerability
  • RPC Locator vulnerability

For more information about these Windows vulnerabilities, please refer to the following Microsoft Web pages:

It attempts to log on to systems using a predefined list of user names and passwords.

It also has backdoor capabilities and may execute malicious commands on the host machine. It terminates antivirus-related processes and dropped files by other malware. It also steals CD keys of certain game applications.

For additional information about this threat, see:

Description created: Apr. 5, 2004 2:01:29 AM GMT -0800


Size of malware: 548,864 Bytes (uncompressed)

Initial samples received on: Apr 5, 2004



This memory-resident worm usually arrives via network shares.

Upon execution, it drops a copy of itself in the Windows system folder as the following file:


(Note: The Windows system folder is usually C:\WINNT\System32 on Windows 2000, and C:\Windows\System32 on Windows XP.)

To enable its automatic execution at every system startup, it creates the following registry entries:

Configuration Loader="ahnhst.exe"

Configuration Loader="ahnhst.exe"

It also adds this registry key for its autostart mechanism:


Network Propagation and Exploits

This worm takes advantage of the Remote Procedure Call (RPC) Distributed Component Object Model (DCOM) vulnerability present on Windows NT systems, which allows an attacker to gain full access and execute any code on a target machine, leaving it compromised.

Read more on this vulnerability from the following link:

It looks for vulnerable machines on the network by scanning for random TCP/IP addresses on port 135.

It further uses the RPC Locator vulnerability which affects Windows NT systems and searches for vulnerable Windows NT machines on the network by incrementally scanning TCP/IP addresses on port 445.

More information on this vulnerability is available from the following Microsoft page:

It also exploits the IIS5/WEBDAV buffer overrun exploit affecting Windows NT platforms, which enables arbitrary codes to execute on the server.

The following link offers more information from Microsoft about this vulnerability:

It also searches for the following network shares:

  • admin$
  • print$
  • c$
  • d$
  • ipc$

If these network shares have full access rights, the worm attempts to drop and execute a copy of itself. If these shares have restricted access, it forces its way into the system using the following user names and passwords:

User names


  • mypass
  • Login
  • owner
  • secret
  • foobar
  • patrick
  • alpha
  • 123abc
  • 1234qwer
  • 123123
  • 121212
  • 111111
  • enable
  • godblessyou
  • ihavenopass
  • 123asd
  • super
  • Internet
  • computer
  • server
  • 123qwe
  • sybase
  • oracle
  • database
  • passwd
  • 88888888
  • 11111111
  • 00000000
  • 000000
  • 54321
  • 654321
  • 123456789
  • 12345678
  • 1234567
  • 123456
  • 12345
  • Password
  • password

Backdoor Capabilities

This malware scans for ports to establish connection with the malware author. It uses Secure Socket Layer (SSL) so that it can encrypt the packets it sends to avoid detection.

It attempts to connects to the IRC server Irc.brokenirc.net and join a channel, where it waits for commands from the malicious user.

It enables the malicious user to do any or all of the following:

  • Change the server where the bot connects to
  • Reconnect to the server
  • Send a message to the IRC server
  • Quit the bot
  • Send a private message
  • Make the bot part a channel
  • Print netinfo
  • Let the bot perform mode change
  • Make the bot join a channel
  • Print netinfo when host matches
  • Print netinfo when the bot is .edu
  • Let the bot perform an action
  • Disconnect the bot from irc
  • Run a command on the system
  • Delete shares/disable DCOM
  • Display system information
  • Make the bot generate a new random nick
  • Open a file
  • Execute an .EXE file
  • Resolve ip/host name by DNS
  • Harvest email addresses from the system
  • Delete/add a service through registry modification
  • Scan port for possible vulnerable systems

Information Theft

This malware steals the Windows Product ID and the CD keys of the following popular games:

Antivirus Retaliation

This worm terminates the following running processes:

Denial of Service

This malware performs denial of service attacks using the following methods:

  • HTTP flood
  • SYN flood
  • UDP flood
  • PING flood

Its target Web sites are as follows:

  • harr0.com
  • www.harr0.com
  • ryan1918.com

Other Details

This malware also terminates the following processes upon execution:

  • winhlpp32.exe
  • tftpd.exe
  • dllhost.exe
  • winppr32.exe
  • mspatch.exe
  • penis32.exe
  • msblast.exe

Analysis by: Gerald T. Carsula

Revision History:

First pattern file version: 4.276.01
First pattern file release date: Feb 15, 2007


Minimum scan engine version needed: 6.500

Pattern file needed: 7.547.00

Pattern release date: Oct 16, 2010

Important note: The "Minimum scan engine" refers to the earliest Trend Micro scan engine version guaranteed to detect this threat. However, Trend Micro strongly recommends that you update to the latest version in order to get comprehensive protection. Download the latest scan engine here.


Restarting in Safe Mode

� On Windows NT (VGA mode)

  1. Click Start>Settings>Control Panel.
  2. Double-click the System icon.
  3. Click the Startup/Shutdown tab.
  4. Set the Show List field to 10 seconds and click OK to save this change.
  5. Shut down and restart your computer.
  6. Select VGA mode from the startup menu.

� On Windows 2000

  1. Restart your computer.
  2. Press the F8 key, when you see the Starting Windows bar at the bottom of the screen.
  3. Choose the Safe Mode option from the Windows Advanced Options Menu then press Enter.

� On Windows XP

  1. Restart your computer.
  2. Press F8 after the Power-On Self Test (POST) is done. If the Windows Advanced Options Menu does not appear, try restarting and then pressing F8 several times after the POST screen.
  3. Choose the Safe Mode option from the Windows Advanced Options Menu then press Enter.

Note: After performing all the solutions for the removal of this malware, please restart your system normally, and run your Trend Micro antivirus product.

Editing the Registry

This malware modifies the system's registry. Users affected by this malware may need to modify or delete specific registry keys or entries. For detailed information regarding registry editing, please refer to the following articles from Microsoft:

  1. HOW TO: Backup, Edit, and Restore the Registry in Windows NT 4.0
  2. HOW TO: Backup, Edit, and Restore the Registry in Windows 2000
  3. HOW TO: Back Up, Edit, and Restore the Registry in Windows XP and 2003

Removing Autostart Entries from the Registry

Removing autostart entries from the registry prevents the malware from executing during startup.

  1. Open Registry Editor. To do this, click Start>Run, type Regedit, then press Enter.
  2. In the left panel, double-click the following:
  3. In the right panel, locate and delete the entry:
    Configuration Loader = �ahnhst.exe�
  4. In the left panel, double-click the following:
  5. In the right panel, locate and delete the entry:
    Configuration Loader = �ahnhst.exe�
  6. Close Registry Editor.
NOTE: If you were not able to terminate the malware process from memory as described in the previous procedure, restart your system.

Disabling Malware Service on Windows NT, 2000, and XP

  1. Restart your machine to terminate the malware service. Next, remove the malware service from the registry.
  2. Open Registry Editor. To do this, click Start>Run, type REGEDIT, then press Enter.
  3. In the left panel, double-click the following: HKEY_LOCAL_MACHINE>SYSTEM>CurrentControlSet>
  4. Right click "svchost" and select "Delete".
  5. Close Registry Editor.

Important Windows ME/XP Cleaning Instructions

Users running Windows ME and XP must disable System Restore to allow full scanning of infected systems.

Users running other Windows versions can proceed with the succeeding procedure set(s).

Running Trend Micro Antivirus

Scan your system with Trend Micro antivirus and delete files detected as WORM_AGOBOT.MX. To do this, Trend Micro customers must download the latest virus pattern file and scan their system. Other Internet users can use HouseCall, Trend Micro's online virus scanner.

Applying Patches

Download the latest patch. Information and download links on the vulnerabilities exploited by the malware can be found at the following links:

Trend Micro offers best-of-breed antivirus and content-security solutions for your corporate network, small and medium business, mobile device or home PC.