WORM_MUMU.B

 Analysis by: Sabrina Lei Sioting

 ALIASES:

Worm:Win32/Mumu.A (Microsoft), Net-Worm.Win32.Muma.c (Kaspersky), W32.Mumu.B.Worm (Symantec), W32/Mumu.b.worm (McAfee), W32/Mumu-C (Sophos), Win32.HLLW.Mumu.A (Fsecure), Worm/Mumu.B.1 (Antivir), W32/Muma.B (Authentium), Win32.HLLW.Mumu.A (Bitdefender), W32/Muma.B (Fprot), Win32/Mumu.B worm (Eset),

 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:

Via network shares

This worm executes the files it drops, prompting the affected system to exhibit the malicious routines they contain.

  TECHNICAL DETAILS

File Size:

294,912 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

06 Mar 2009

Payload:

Drops files

Arrival Details

This worm may arrive via network shares.

Installation

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

  • %System%\mumu.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.)

It drops the following component file(s):

  • %System%\IPCPass.txt

(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.)

It drops the following non-malicious file:

  • %System%\psexec.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.)

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • qjinfo2mutex
  • qjinfo1mutex

Other System Modifications

This worm adds the following registry entries as part of its installation routine:

HKEY_LOCAL_MACHINE\SOFTWARE\mumu
{first 3 octet of the machine's IP address} = "{random hex} "

It adds the following registry keys as part of its installation routine:

HKEY_LOCAL_MACHINE\SOFTWARE\mumu

Dropping Routine

This worm drops the following files:

  • %System%\kavfind.exe - detected as TROJ_HACLINE.A
  • %System%\last.exe - detected as TROJ_MUMUBOY.C

(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.)

It executes the files it drops, prompting the affected system to exhibit the malicious routines they contain.

NOTES:

Once it found a vulnerable machine from the network, it copies itslef to Admin$\system32 as mumu.exe.

It uses the legitimate program PSEXEC.EXE from Sysinternals to remotely run the copied program using the following command:

  • start /i /min /wait /B psexec \\%target_pc% -u %username% -p %password% -d mumu.exe

This time, %username% and %password% are the ones saved in IPCFind.txt from TROJ_HACLINE.A. The program runs non-interactively with the switch d.

It deletes the log file IPCFind.txt afterwards.

Aside from IP scanning for target machines, it also tries to replicate on connected machines, usually those locally attached to the infected system. It executes the following command for one minute to get the established connections and saves to A.TMP file:

  • CMD /c netstat -n|find \":\" >A.TMP

It sends a PING command to every machine and considers the string reply as a success reply. The PING output is temporarily saved to B.TMP file.

When connection is successful, it copies the worm to other machines as Admin$\Winnt\MUMU.EXE and runs it. It deletes the A.TMP and B.TMP files after the routine.

It opens the file QJINFO.INI from TROJ_MUMUBOY.C. If the file is not empty, it sleeps for 5 seconds before it maps the file in Windows memory for easy access. It then proceeds to its SMTP routine. The worm lacks some error checking in SMTP routine, causing it to crash once in a while if certain error occurs.

The worm contains SMTP (Simple Mail Transfer Protocol) commands to connect to the SMTP server, smtp.{BLOCKED}a.com.cn.

It generates an email with the following details:


To: {BLOCKED}0.student@sina.com
From: {BLOCKED}il2.student@sina.com
Subject: {random number}{Computer Name}
Date: {Current Date}

It also creates a pop-up child window with the class name, SYSTARY and then modifies the registry as follows:

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

  SOLUTION

Minimum Scan Engine:

9.200

VSAPI OPR PATTERN File:

5.883.00

VSAPI OPR PATTERN Date:

06 Mar 2009

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_MUMU.B

     TROJ_HACLINE.A
    TROJ_MUMUBOY.C

Step 3

Terminate the malware/grayware/spyware process:

[ Learn More ]
  • For Windows 98 and ME users, Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  • 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.
  • 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 key

    [ 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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

    • In HKEY_LOCAL_MACHINE\SOFTWARE
      • mumu

    Step 5

    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%\IPCPass.txt
    %System%\psexec.exe

    Step 6

    Scan your computer with your Trend Micro product to delete files detected as WORM_MUMU.B. 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.


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