1. Symantec/
  2. Security Response/
  3. Infostealer.Monstres


Risk Level 1: Very Low

August 16, 2007
August 24, 2007 8:56:23 PM
Also Known As:
Spy-Agent.bw [McAfee], Troj/Bancos-BDR [Sophos], Spy-Agent.cj.gen.h [McAfee], Troj/Zbot-F [Sophos], Troj/Agent-HEF [Sophos], Troj/Zbot-AB [Sophos], Troj/Agent-HFZ [Sophos]
Infection Length:
153,600 bytes
Systems Affected:
When the Trojan is executed, it creates the following mutex to ensure that only one copy of the threat is running on the computer:

It checks for the presence of the following firewall programs:

Next, the Trojan copies itself to the following location and appends a random amount of data to the file in order to have a random size:

It creates the following folder with system and hidden attributes:

The Trojan then creates the following files, the first of which is used to save gathered information and the second is used to store the encrypted configuration of the Trojan:
  • %System%\wsnpoem\audio.dll
  • %System%\wsnpoem\video.dll

Next, the Trojan creates the following registry entry:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\"pathx" = [MALWARE_ORIGINAL_FILENAME]

It also modifies the following registry entry so that it executes whenever Windows starts:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\"Userinit" = "%System%\userinit.exe, %System%\ntos.exe"

Next, it injects malicious code into the following running processes:

It attempts to create a malicious thread in all running processes except for the following one:

The Trojan creates some of the following mutexes to synchronize all active threads while running in memory:
  • __SYSTEM__23D80F10__
  • __SYSTEM__45A2F601__
  • __SYSTEM__7F4523E5__
  • __SYSTEM__91C38905__
  • __SYSTEM__64AD0625__

The injected code will prevent the removal of the Trojan by blocking access and deletion of all of the malicious files and by regenerating all of the registry subkeys associated with the Trojan when they are deleted.

Next, it may add the following registry entries as infection markers for the compromised computer:
HKEY_LOCAL_MACHINE\Software\microsoft\windows nt\currentversion\network\"UID" = "[COMPUTERNAME]_[UNIQUE_ID]"

It then hooks the following system functions of NTDLL.DLL using rootkit techniques to ensure that its code gets injected into each process:
  • NtCreateThread
  • LdrLoadDll
  • LdrGetProcedureAddress

The Trojan attempts to hook the following functions in the WININET.DLL library to have control of network functionalities and to steal sensitive information:
  • HttpSendRequestW
  • HttpSendRequestA
  • HttpSendRequestExW
  • HttpSendRequestExA
  • InternetReadFile
  • InternetReadFileExW
  • InternetReadFileExA
  • InternetQueryDataAvailable
  • InternetCloseHandle

It attempts to hook the following functions in the WS2_32.DLL and WSOCK32.DLL libraries to have control of network functionalities and to steal sensitive information:
  • send
  • sendto
  • closesocket
  • WSASend
  • WSASendTo

The Trojan may perform the following actions when visiting the Web sites:
  • Intercept network traffic
  • Redirect traffic
  • Steal sensitive data

The Trojan can steal sensitive information from the monster.com Web site by using an employer/recruiter account which is provided by an attacker. It downloads the details for the account from the following location:
http://[REMOTE SERVER]/mnstr/grabv2.php?getid=1

Next, the Trojan logs in to the following monster.com Web sites using the provided account:
  • http://recruiter.monster.com
  • http://hiring.monster.com

It then searches for all available resumes, stealing the following information from each resume:
  • Name
  • Email address
  • Home address
  • Mobile and home phone numbers

Next, it attempts to post the stolen information to the following Web site:
http://[REMOTE SERVER]/grabv2.php

The Trojan may contact the following site to get instructions for spam and additional configuration information:

It sends spam email and attempts to contact the following SMTP server:


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: Elia Florio
Summary| Technical Details| Removal

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