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Infostealer.Banker.C

Risk Level 1: Very Low

Discovered:
April 2, 2007
Updated:
August 16, 2012 11:38:29 AM
Also Known As:
Troj/Bancos-BBT [Sophos], Troj/Bancos-BCV [Sophos], Trojan-Downloader.Win32.Agent.bvz [Kaspersky], Win32/Kollah.KX [Computer Associates], TROJ_ZBOT.AJC [Trend], TROJ_ZBOT.US [Trend]
Type:
Trojan
Infection Length:
34,304 bytes
Systems Affected:
Windows 2000, Windows 95, Windows 98, Windows Me, Windows NT, Windows Server 2003, Windows XP
It has been reported that this threat may arrive with a spoofed email, which pretends to be an update for customers sent by ABN-AMRO bank.

The e-mail is written in Dutch and has the following characteristics:

From:
support@abnamro.nl

Subject:
Vernieuw uw Internet-browser met SSL3 zo spoedig mogelijk.

Attachment:
ms_ssl3_upd.exe

When the Trojan is executed, it creates one of the following mutexes to ensure that only one copy of the threat is running on the computer:
  • __SYSTEM__64AD0625__
  • _AVIRA_21099


It checks for the presence of the following firewall programs:
  • ZLCLIENT.EXE
  • OUTPOST.EXE


It then gathers the following information from the compromised computer:
  • OS version
  • Presence of Service Pack 2
  • Language of the system


Next, the Trojan copies itself to one of the following locations and appends a random amount of data to the file in order to have a random size:
  • %System%\ntos.exe
  • %System%\sdra64.exe


It creates one of the following folders with system and hidden attributes:
  • %System%\wsnpoem
  • %System%\lowsec


The Trojan may then create some of 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
  • %System%\lowsec\local.ds
  • %System%\lowsec\user.ds


Next, the Trojan creates the following registry entries so that it executes whenever Windows starts:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run\"userinit" = "%System%\ntos.exe"
HKEY_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\Run\"userinit" = "%System%\ntos.exe"

It also modifies one of the following registry entries so that it executes whenever Windows starts:
  • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\"Userinit" = "%System%\userinit.exe, %System%\ntos.exe"
  • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\"Userinit" = "%System%\userinit.exe, %System%\sdra64.exe"


Next, it injects malicious code into the following running processes:
  • WINLOGON.EXE
  • SVCHOST.EXE
  • EXPLORER.EXE


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

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__
  • _AVIRA_2110
  • _AVIRA_2101
  • _AVIRA_2108
  • _AVIRA_2109


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]"
  • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\"{6780A29E-6A18-0C70-1DFF-1610DDE00108}" = "[HEXADECIMAL VALUE]"
  • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\"{F710FA10-2031-3106-8872-93A2B5C5C620}" = "[HEXADECIMAL VALUE]"


The Trojan deletes cookies in the Internet Explorer URL cache so that users will have to re-insert passwords when logging into banking Web sites.

It reads PStore to steal saved passwords on the compromised computer.

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


It also attempts to hook the following functions in the USER32.DLL library to have control of network functionalities and to steal sensitive information:
  • GetMessageW
  • GetMessageA
  • PeekMessageW
  • PeekMessageA
  • GetClipboardData


The Trojan may modify the content of the %System%\drivers\etc\hosts file.

The Trojan may perform the following actions:
  • Intercept network traffic
  • Intercept keyboard input
  • Steal information from Windows clipboard
  • Capture screenshots
  • Redirect traffic


The Trojan is configured to search for specific keywords in URLs and also in HTTP packets. The default configuration includes the following strings to be searched, where asterisk (*) means a wild card:
  • *Tan*
  • *Schmetterling*
  • *berweisung*
  • *Amount*
  • *tanentry*
  • *RESULT2*
  • *citibank.de/*
  • I2=*&H0=DT
  • *banking.*/cgi/ueber*.cgi*
  • ###=######&tid=*
  • [https://]onlineeast.bankofamerica.com/cgi-bin/ias/*/GotoW[REMOVED]
  • CustomerServiceMenuEntryPoint?custAction=75
  • bankofamerica.com/cgi-bin/ias/*/GotoWelcome
  • *<input *value="
  • *<option selected'
  • *<select


It downloads an additional encrypted configuration file from one of the following URLs and saves it to %System%\video.dll:
  • 81.95.148.244/911/cfg2.bin
  • [http://]basdzsdas.com/poker/config.bin


At the time of writing, the decrypted configuration contains some the following strings to be searched by the Trojan:
  • [https://]extranet.banesto.es/*/loginParti[REMOVED]
  • [https://]banesnet.banesto.es/*/loginEmp[REMOVED]
  • [https://]empresas.gruposantander.es/WebEmpresas/servlet/webempresa[REMOVED]
  • [https://]banca.cajaen.es/Jaen/C@JAENdi[REMOVED]
  • [https://]www.cajavital.es/Appserver/vita[REMOVED]
  • [https://]www.cajalaboral.com*/home/acces[REMOVED]
  • [https://]cipehb*.cdg.citibank.de/HomeBankingSecure/Pers/StartSes[REMOVED]


The Trojan may upload the gathered information to a remote site by using FTP protocol.

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: Elia Florio and Sean Kiernan
Summary| Technical Details| Removal

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