Malware type: Backdoor

Aliases: Backdoor.Win32.IRCBot.gen (Kaspersky), Backdoor.Sdbot (Symantec), W32/Sdbot-Fam (Sophos),

In the wild: No

Destructive: No

Language: English

Platform: Windows 95, 98, ME, NT, 2000, XP

Encrypted: Yes

Overall risk rating:

Reported infections:

Damage potential:


Distribution potential:


This backdoor Trojan connects to an Internet Relay Chat (IRC) channel where it receives commands from a hacker. It can then perform the following actions, consequently compromising network security:

  • Obtain system information
  • Download files
  • Upload files
  • Redirect connections
  • Perform a Distributed Denial of Service (DDoS) attack on a target machine

It runs on Windows 95, 98, ME, NT, 2000 and XP.

For additional information about this threat, see:

Description created: Oct. 30, 2003 11:40:48 AM GMT -0800
Description updated: Mar. 8, 2005 2:04:11 AM GMT -0800


Size of malware: 13,856 Bytes (Compressed)
34,324 Bytes (Uncompressed)

Initial samples received on: Oct 30, 2003

Payload 1: Compromise network security

Trigger condition 1: Always


Upon execution, this memory-resident malware drops a copy of itself in the Windows system folder as the any of the following file names?


To enable itself to run at every system startup, it adds the following registry entries:



Backdoor Capabilities

This malware connects to a remote Internet Relay Chat (IRC) server and joins a specified channel. It then obtains commands from a hacker and performs actions that compromises network security.

This backdoor Trojan is capable of doing the following:

  • Obtain system information such as:
    • CPU speed
    • Total memory
    • Free memory
    • Windows version
    • Currently logged in user
    • Total uptime
    • Connection type
  • Download files
  • Upload files
  • Redirect connections
  • Perform a Distributed Denial of Service (DDoS) attack on a target machine by ping flooding or flooding a specified UDP port with large amount of data.

If the dropped file is Webprint.exe, it connects to ww1.gfgfgt.com, which is currently inaccessible. It opens a random port to connect to this site.

It attempts to connect to the channel ww1 and connect as bud. If successful, a remote user may then send commands to the compromised system.

Other Details

Its process cannot be seen on Windows 95/98/ME taskbar. It arrives UPX-compressed.

Analysis by: Doris Pagauitan

Revision History:

First pattern file version: 676
First pattern file release date: Oct 30, 2003


Minimum scan engine version needed: 5.600

Pattern file needed: 5.541.00

Pattern release date: Sep 14, 2008

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.


Identifying the Malware Program

To remove this malware, first identify the malware program.

  1. Scan your system with your Trend Micro antivirus product.
  2. NOTE all files detected as BKDR_SDBOT.W.

Trend Micro customers need to download the latest pattern file before scanning their system. Other Internet users may use Housecall, Trend Micro�s free online virus scanner.

Terminating the Malware Program

This procedure terminates the running malware process from memory. You will need the name(s) of the file(s) detected earlier.

  1. Open Windows Task Manager.
    On Windows 95/98/ME systems, press
    On Windows NT/2000/XP systems, press
    CTRL%20SHIFT%20ESC, then click the Processes tab.
  2. In the list of running programs*, locate the following malware files:
  3. Select one of the detected files, then press either the End Task or the End Process button, depending on the version of Windows on your system.
  4. Do the same for all detected malware files in the list of running processes.
  5. To check if the malware process has been terminated, close Task Manager, and then open it again.
  6. Close Task Manager.

*NOTE: On systems running Windows 95/98/ME, Task Manager may not show certain processes. You may use a third party process viewer to terminate the malware process. Otherwise, continue with the next procedure, noting additional instructions.

Removing Autostart Entries from the Registry

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

To remove the malware autostart entries:

  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:
  4. In the left panel, double-click the following:
  5. In the right panel, locate and delete the entry:
  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.

Additional Windows ME/XP Cleaning Instructions

Running Trend Micro Antivirus

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

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