ALIASES:

PWS:Win32/Zbot (Microsoft); Trojan-FFBJ!F1271D294412 (McAfee); Trojan.Asprox.B (Symantec); Trojan.Win32.Inject.tbrw (Kaspersky); Troj/Msil-ANY (Sophos); Trojan.Win32.Generic!BT (Sunbelt); Trojan horse MSIL5.ACBH (AVG)

 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It deletes itself after execution.

  TECHNICAL DETAILS

File Size: 335,360 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 04 Nov 2014

Arrival Details

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This backdoor creates the following folders:

  • %User Temp%\Cauva
  • %User Profile%\Microsoft\Address Book

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.. %User Profile% is a user's profile folder, where it usually is C:\Documents and Settings\{user name} on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name} on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

Autostart Technique

This backdoor adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Anyj = "%User Temp%\Cauva\anyj.exe "

Other System Modifications

This backdoor adds the following registry keys:

HKEY_CURRENT_USER\Software\Zaxeubu

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\Active Directory GC

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\Bigfoot

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\VeriSign

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\WhoWhere

HKEY_CURRENT_USER\Software\Microsoft\
WAB\WAB4\Wab File Name

It adds the following registry entries:

HKEY_CURRENT_USER\Software\Zaxeubu
e6c1700 = "8xLkgw==?_CHAR(0x03)_?"

HKEY_CURRENT_USER\Software\Zaxeubu
1cd9b8ee = "gBLXgw==×_CHAR(0x03)_eI?Y?Y´"

HKEY_CURRENT_USER\Software\Zaxeubu
1cd9b8ee = "gRLXgw==?_CHAR(0x03)_?"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\Active Directory GC
LDAP Server ID = "0"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\Bigfoot
LDAP Server ID = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\VeriSign
LDAP Server ID = "2"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\WhoWhere
LDAP Server ID = "3"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager
Server ID = "4"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts
PreConfigVer = "4"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts
PreConfigVerNTDS = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\Active Directory GC
Account Name = "Active Directory"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\Active Directory GC
LDAP Server = "NULL"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\Active Directory GC
LDAP Search Return = "64"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\Active Directory GC
LDAP Timeout = "3c"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\Active Directory GC
LDAP Authentication = "2"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\Active Directory GC
LDAP Simple Search = "0"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\Active Directory GC
LDAP Bind DN = "0"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\Active Directory GC
LDAP Port = "cc4"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\Active Directory GC
LDAP Resolve Flag = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\Active Directory GC
LDAP Secure Connection = "0"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\Active Directory GC
LDAP User Name = "NULL"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\Active Directory GC
LDAP Search Base = "NULL"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\Bigfoot
Account Name = "Bigfoot Internet Directory Service"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\Bigfoot
LDAP Server = "ldap.bigfoot.com"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\Bigfoot
LDAP URL = "http://www.{BLOCKED}t.com"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\Bigfoot
LDAP Search Return = "64"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\Bigfoot
LDAP Timeout = "3c"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\Bigfoot
LDAP Authentication = "0"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\Bigfoot
LDAP Simple Search = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\Bigfoot
LDAP Logo = "%ProgramFiles%\Common Files\Services\bigfoot.bmp"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\VeriSign
Account Name = "VeriSign Internet Directory Service"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\VeriSign
LDAP Server = "directory.verisign.com"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\VeriSign
LDAP URL = "http://www.{BLOCKED}gn.com"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\VeriSign
LDAP Search Return = "64"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\VeriSign
LDAP Timeout = "3c"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\VeriSign
LDAP Authentication = "0"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\VeriSign
LDAP Search Base = "NULL"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\VeriSign
LDAP Simple Search = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\VeriSign
LDAP Logo = "%ProgramFiles%\Common Files\Services\verisign.bmp"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\WhoWhere
Account Name = "WhoWhere Internet Directory Service"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\WhoWhere
LDAP Server = "ldap.whowhere.com"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\WhoWhere
LDAP URL = "http://www.{BLOCKED}re.com"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\WhoWhere
LDAP Search Return = "64"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\WhoWhere
LDAP Timeout = "3c"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\WhoWhere
LDAP Authentication = "0"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\WhoWhere
LDAP Simple Search = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\WhoWhere
LDAP Logo = "%ProgramFiles%\Common Files\Services\whowhere.bmp"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager
Default LDAP Account = "Active Directory GC"

HKEY_CURRENT_USER\Software\Microsoft\
WAB\WAB4
OlkContactRefresh = "0"

HKEY_CURRENT_USER\Software\Microsoft\
WAB\WAB4
OlkFolderRefresh = "0"

HKEY_CURRENT_USER\Identities\{8A24C031-62FE-4BF5-94F0-BFD4FBCD674B}
Identity Ordinal = "1"

HKEY_CURRENT_USER\Software\Zaxeubu
1cd9b8ee = "83d712c1"

It modifies the following registry entries:

HKEY_CURRENT_USER\Identities
Identity Ordinal = "2"

(Note: The default value data of the said registry entry is 1.)

Dropping Routine

This backdoor drops the following files:

  • %User Temp%\Cauva\anyj.exe
  • %User Profile%\Application Data\tygynu.vyf
  • %User Profile%\Address Book\Wilbert.wab

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.. %User Profile% is a user's profile folder, where it usually is C:\Documents and Settings\{user name} on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name} on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

Other Details

This backdoor connects to the following possibly malicious URL:

  • {BLOCKED}0.1

It deletes itself after execution.

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine: 9.700

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Restart in Safe Mode

[ Learn More ]

Step 3

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.

  • In HKEY_CURRENT_USER\Software
    • Zaxeubu
  • In HKEY_CURRENT_USER\Software\Microsoft
    • Internet Account Manager
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager
    • Accounts
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts
    • Active Directory GC
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts
    • Bigfoot
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts
    • VeriSign
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts
    • WhoWhere
  • In HKEY_CURRENT_USER\Software\Microsoft\WAB\WAB4
    • Wab File Name

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Anyj = "%User Temp%\Cauva\anyj.exe "
  • In HKEY_CURRENT_USER\Software\Zaxeubu
    • e6c1700 = "8xLkgw==?_CHAR(0x03)_?"
  • In HKEY_CURRENT_USER\Software\Zaxeubu
    • 1cd9b8ee = "gBLXgw==×_CHAR(0x03)_eI?Y?Y´"
  • In HKEY_CURRENT_USER\Software\Zaxeubu
    • 1cd9b8ee = "gRLXgw==?_CHAR(0x03)_?"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\Active Directory GC
    • LDAP Server ID = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\Bigfoot
    • LDAP Server ID = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\VeriSign
    • LDAP Server ID = "2"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\WhoWhere
    • LDAP Server ID = "3"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager
    • Server ID = "4"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts
    • PreConfigVer = "4"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts
    • PreConfigVerNTDS = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\Active Directory GC
    • Account Name = "Active Directory"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\Active Directory GC
    • LDAP Server = "NULL"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\Active Directory GC
    • LDAP Search Return = "64"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\Active Directory GC
    • LDAP Timeout = "3c"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\Active Directory GC
    • LDAP Authentication = "2"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\Active Directory GC
    • LDAP Simple Search = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\Active Directory GC
    • LDAP Bind DN = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\Active Directory GC
    • LDAP Port = "cc4"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\Active Directory GC
    • LDAP Resolve Flag = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\Active Directory GC
    • LDAP Secure Connection = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\Active Directory GC
    • LDAP User Name = "NULL"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\Active Directory GC
    • LDAP Search Base = "NULL"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\Bigfoot
    • Account Name = "Bigfoot Internet Directory Service"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\Bigfoot
    • LDAP Server = "ldap.bigfoot.com"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\Bigfoot
    • LDAP URL = "http://www.{BLOCKED}t.com"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\Bigfoot
    • LDAP Search Return = "64"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\Bigfoot
    • LDAP Timeout = "3c"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\Bigfoot
    • LDAP Authentication = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\Bigfoot
    • LDAP Simple Search = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\Bigfoot
    • LDAP Logo = "%ProgramFiles%\Common Files\Services\bigfoot.bmp"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\VeriSign
    • Account Name = "VeriSign Internet Directory Service"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\VeriSign
    • LDAP Server = "directory.verisign.com"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\VeriSign
    • LDAP URL = "http://www.{BLOCKED}gn.com"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\VeriSign
    • LDAP Search Return = "64"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\VeriSign
    • LDAP Timeout = "3c"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\VeriSign
    • LDAP Authentication = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\VeriSign
    • LDAP Search Base = "NULL"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\VeriSign
    • LDAP Simple Search = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\VeriSign
    • LDAP Logo = "%ProgramFiles%\Common Files\Services\verisign.bmp"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\WhoWhere
    • Account Name = "WhoWhere Internet Directory Service"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\WhoWhere
    • LDAP Server = "ldap.whowhere.com"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\WhoWhere
    • LDAP URL = "http://www.{BLOCKED}re.com"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\WhoWhere
    • LDAP Search Return = "64"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\WhoWhere
    • LDAP Timeout = "3c"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\WhoWhere
    • LDAP Authentication = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\WhoWhere
    • LDAP Simple Search = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts\WhoWhere
    • LDAP Logo = "%ProgramFiles%\Common Files\Services\whowhere.bmp"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager
    • Default LDAP Account = "Active Directory GC"
  • In HKEY_CURRENT_USER\Software\Microsoft\WAB\WAB4
    • OlkContactRefresh = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\WAB\WAB4
    • OlkFolderRefresh = "0"
  • In HKEY_CURRENT_USER\Identities\{8A24C031-62FE-4BF5-94F0-BFD4FBCD674B}
    • Identity Ordinal = "1"
  • In HKEY_CURRENT_USER\Software\Zaxeubu
    • 1cd9b8ee = "83d712c1"

Step 5

Restore these modified registry values

[ Learn More ]

Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.

  • In HKEY_CURRENT_USER\Identities
    • From: Identity Ordinal = "2"
      To: Identity Ordinal = ""1""

Step 6

Search and delete these components

[ Learn More ]
There may be some components 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.
  • %User Temp%\Cauva\anyj.exe
  • %User Profile%\Application Data\tygynu.vyf
  • %User Profile%\Address Book\Wilbert.wab

Step 7

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %User Temp%\Cauva
  • %User Profile%\Microsoft\Address Book

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_ANDROM.YYKC. 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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