Analysis by: Karl Dominguez


Windows 2000, Windows XP, Windows Server 2003


  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes


Infection Channel:

Propagates via software vulnerabilities

This worm may be downloaded by other malware/grayware/spyware from remote sites. It may be unknowingly downloaded by a user while visiting malicious websites.



TCP port 445 (Microsoft-DS)

File Size:

57,344 bytes

File Type:


Memory Resident:


Initial Samples Received Date:

04 Mar 2010


Steals information, Drops files

Arrival Details

This worm may arrive via network shares.

It may be downloaded by other malware/grayware/spyware from remote sites.

It may be unknowingly downloaded by a user while visiting malicious websites.


This worm drops the following component file(s):

  • %System%\lsasvc.exe - detected as TROJ_AGENT.AYAA

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

Autostart Technique

This worm adds the following registry entries to enable its automatic execution at every system startup:

Windows Update = {malware path}\{malware file name}

Other Details

For more information on the aforementioned vulnerabilities, please see the following pages:

  • (MS08-067) Vulnerability in Server Service Could Allow Remote Code Execution (958644)

Information Theft Routine

This worm sends the IP address and Windows OS of the infected system to the remote user via email. It send these information using "gmail-smtp-in.l.google.com" or its own Simple Mail Transfer Protocol (SMTP) with the following format:

Subject: {IP address of the infected system}|{Windows OS}
From: {BLOCKED}03@yahoo.com
To: {BLOCKED}001@gmail.com
Message body: none

Propagation via Software Vulnerabilities

This worm takes advantage of the following software vulnerabilities to propagate across networks:
  • Microsoft Security Bulletin MS08-067

It generates random IP address and attempts to establish a connection using TCP port 445. Once established, it uses the NetUserEnum API to gather the list of user accounts of the vulnerable system then executes a brute force dictionary attack to access the system. It uses the following credentials:
  • User name:
    • Administrator
  • Passwords:
    • 1
    • 12
    • 123
    • 1111
    • 1234
    • 4321
    • 12345
    • 54321
    • 111111
    • 123456
    • 654321
    • 1234567
    • !@#$
    • !@#$%^;
    • !@#$%
    • !@#$%^;
    • !@#$%^
    • !@#$%^;*()
    • !@#$%^;*(
    • admin
    • angel
    • asdf
    • asdfg
    • asdfgh
    • BUMBLE
    • mail
    • passwd
    • password
    • pass
    • root
    • test1234
    • web
    • ~!@#$%^;*()_+

Once it gains access on the infected system, it drops a copy of itself as CSRSS.EXE in the ADMIN$ folder. It also deletes sharing permissions of the following folders:
  • ADMIN$
  • C$


Minimum Scan Engine:





04 Mar 2010

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Remove malware files dropped/downloaded by WORM_MYDOOM.SMB

Step 3

Identify and terminate files detected as WORM_MYDOOM.SMB

[ Learn More ]
  1. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  2. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 4

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Windows Update = {malware path}\{malware file name}

Step 5

Scan your computer with your Trend Micro product to delete files detected as WORM_MYDOOM.SMB. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.

Step 6

Download and apply these security patches Refrain from using these products until the appropriate patches have been installed. Trend Micro advises users to download critical patches upon release by vendors.

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