WORM_MYDOOM.DA

 Analysis by: Sabrina Lei Sioting

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Propagates via software vulnerabilities, Propagates via network shares

This worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It opens certain ports to access shared networks. It takes advantage of software vulnerabilities to propagate across networks.

  TECHNICAL DETAILS

Ports:

TCP port 445 (Microsoft-DS)

File Size:

57,344 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

10 Nov 2011

Payload:

Steals information

Arrival Details

This worm may arrive via network shares.

It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This worm drops the following copies of itself into the affected system:

  • %System Root%\csrss.exe

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Windows Update = "{malware path}\{malware name}.exe"

Propagation

This worm opens the following ports to access shared networks:

  • TCP port 445

It uses the following user name and password to gain access to password-protected shares:

  • User name: administrator
  • Password: {any of the following}
    • !@#$%
    • &*()_+
    • 111111
    • 12345
    • 123456
    • 1234567
    • 54321
    • 654321
    • BUMBLE
    • admin
    • angel
    • asdfg
    • asdfgh
    • mail1
    • mail123
    • mail1234
    • passwd
    • password
    • test1234
    • web123
    • web1234
    • ~!@#$%

It takes advantage of the following software vulnerabilities to propagate across networks:

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

Dropping Routine

This worm drops the following files:

  • %System%\lsasvc.exe

(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.)

NOTES:

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

  • ADMIN$
  • C$

This worm sends the IP address and Windows OS of the infected system to the remote user via email. It sends the information using the Simple Mail Transfer Protocol (SMTP) gmail-smtp-in.l.google.com; or its own SMTP engine. The email it sends has 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

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

7.610.01

FIRST VSAPI PATTERN DATE:

10 Nov 2011

VSAPI OPR PATTERN File:

7.611.00

VSAPI OPR PATTERN Date:

11 Nov 2011

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

Identify and terminate files detected as WORM_MYDOOM.DA

[ 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 3

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 name}.exe"

Step 4

Search and delete these files

[ Learn More ]
There may be some component files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %System%\lsasvc.exe

Step 5

Scan your computer with your Trend Micro product to delete files detected as WORM_MYDOOM.DA. 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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