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  3. W32.Morto.B

W32.Morto.B

Risk Level 2: Low

Discovered:
July 9, 2012
Updated:
September 21, 2012 10:05:30 AM
Also Known As:
Worm.Win32.Fipp.a [Kaspersky], PE_MUSTAN.A [Trend]
Type:
Worm
Infection Length:
Varies
Systems Affected:
Windows 2000, Windows 7, Windows 95, Windows 98, Windows Me, Windows NT, Windows Server 2003, Windows Server 2008, Windows Vista, Windows XP
When the worm executes, it injects itself into the following service:
svchost.exe

It makes a copy of %System%\wmicuclt.exe and moves it to the following location:
%System%\wmicuclt

The worm then copies %System%\wscript.exe to the following location:
%System%\wmicuclt.exe

The worm infects the following file by injecting itself into the last section of the file:
%System%\wmicuclt.exe

Note: The worm may also infect other executable files on the compromised computer.

The worm creates the following mutex so that only one instance of the worm runs on the compromised computer:
Global\_PPIftSvc

It creates the following registry entries to register itself as a system service:
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\wmicucltsvc\Security\"Security" = "[WORM BODY IN HEXADECIMAL CHARACTERS]"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\wmicucltsvc\"WOW64" = "2"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\wmicucltsvc\"Start" = "2"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\wmicucltsvc\"ErrorControl" = "0"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\wmicucltsvc\"Type" = "20"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\wmicucltsvc\"ObjectName" = "Local System"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SafeBoot\Minimal\wmicucltsvc\"(Default)" = "Service"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\wmicucltsvc\"Description" = "Stores security information for local user accounts."
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\wmicucltsvc\"DisplayName" = "Remote Access Connection Service"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\wmicucltsvc\"ImagePath" = "%System%\wmicuclt.exe"

It also creates the following registry entries to store data as well as a copy of itself:
  • HKEY_LOCAL_MACHINE\SYSTEM\Select\"v" = "[WORM BODY]"
  • HKEY_LOCAL_MACHINE\SYSTEM\Select\"p" = "[DATA]"
  • HKEY_LOCAL_MACHINE\SYSTEM\Select\"pu" = "[DATA]"

It then modifies the following registry entries to disable certain system settings:
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Windows\"NoPopUpsOnBoot" = "1"
  • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\Windows Error Reporting\"DontshowUI" = "1"

It also modifies the following registry entries to disable security-related applications:
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\360rp\"Start" = "4"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\zhudongfangyu\"Start" = "4"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\ekrn\"Start" = "4"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\MsMpSvc\"Start" = "4"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\V3 Service\"Start" = "4"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\AntiVirService\"Start" = "4"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\a2AntiMalware\"Start" = "4"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\FSORSPClient\"Start" = "4"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\FSMA\"Start" = "4"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\F-Secure Gatekeeper Handler Starter\"Start" = "4"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\kxescore\"Start" = "4"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\kxesapp\"Start" = "4"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\AVGwd\"Start" = "4"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\AVGIDSAgent\"Start" = "4"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\NIS\"Start" = "4"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\avast! Antivirus\"Start" = "4"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\vsserv\"Start" = "4"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\mcshield\"Start" = "4"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\mcods\"Start" = "4"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\amsp\"Start" = "4"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\RsRavMon\"Start" = "4"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\SavService\"Start" = "4"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\PavFnSvr\"Start" = "4"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\pavsrv\"Start" = "4"

It also deletes certain security-related applications if found on the compromised computer.

The worm attempts to open the Remote Desktop Protocol (RDP) connection on computers in the local network by using common user name and password combinations.

Once connected, it opens the default RDP file share created on the compromised computer to access computers on the network:
\\tsclient

It installs itself on remote computers by using the following commands:
  • rundll32 \\tsclient\a\a.dll a
  • regedit /s \\tsclient\a\r.reg

The worm also attempts to spread by copying itself to removable drives.

Next, the worm may attempt to download potentially malicious files from the following remote locations:
  • d.ppns.info
  • e.ppift.net
  • e.ppift.com
  • e.ppift.in

Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
  • Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
  • Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.
Writeup By: Alan Neville
Summary| Technical Details| Removal

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