BKDR_AZBREG.AR

 Analysis by: Mark Joseph Manahan

 ALIASES:

Trojan:Win32/Ramnit.A (Microsoft), a variant of Win32/Kryptik.ANAA trojan (Eset), Backdoor.Win32.Azbreg (Ikarus), W32/Azbreg.ARS!tr (Fortinet)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • 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 registry entries related to antivirus programs. Doing this allows this malware to execute its routines without being detected by installed antivirus programs.

  TECHNICAL DETAILS

File Size:

95,200 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

31 Oct 2012

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 adds the following folders:

  • %Application Data%\{random folder name}

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Windows\Profiles\{user name}\Application Data on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Application Data on Windows NT, and C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003.)

It drops the following copies of itself into the affected system:

  • %User Temp%\{random}.exe
  • %User Startup%\{random}.exe
  • %Application Data%\{random folder name}\{random}.exe

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003.. %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.. %Application Data% is the current user's Application Data folder, which is usually C:\Windows\Profiles\{user name}\Application Data on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Application Data on Windows NT, and C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003.)

It adds the following possibly malicious files or file components:

  • {All Users' Profile}\Application Data\{random 1}.log
  • %Application Data%\{random 2} .log
  • %Application Data%\{random 3} .log
  • %Application Data%\{random 4}
  • %User Temp%\{random}.sys

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Windows\Profiles\{user name}\Application Data on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Application Data on Windows NT, and C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003.. %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003.)

Autostart Technique

This backdoor registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Micorsoft Windows Service
ImagePath = %User Temp%\{random}.sys

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random} = "%Application Data\{random folder name}\{random}.exe"

It modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Userinit = "%System%\userinit.exe,,%Application Data\{random folder name}\{random}.exe"

(Note: The default value data of the said registry entry is "%System%\userinit.exe," .)

Other System Modifications

This backdoor adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Micorsoft Windows Service

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_MICORSOFT_WINDOWS_SERVICE

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Security Center
UacDisableNotify = "1"

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Security Center
AntiVirusOverride = "1"

(Note: The default value data of the said registry entry is "0".)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Security Center
FirewallDisableNotify = "1"

(Note: The default value data of the said registry entry is "0".)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Security Center
AntiVirusDisableNotify = "1"

(Note: The default value data of the said registry entry is "0".)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Security Center
FirewallOverride = "1"

(Note: The default value data of the said registry entry is "0".)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Security Center
UpdatesDisableNotify = "1"

(Note: The default value data of the said registry entry is "0".)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wscsvc
Start = "4"

(Note: The default value data of the said registry entry is "2".)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wuauserv
Start = "4"

(Note: The default value data of the said registry entry is "2".)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile
EnableFirewall = "0"

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

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile
DisableNotifications = "1"

(Note: The default value data of the said registry entry is "0".)

It deletes the following registry entries related to antivirus and security applications:

HKEY_LOCAL_MACHINE\Microsoft\Windows\
CurrentVersion\Run
Windows Defender = "{windows defender path}"

It deletes the following registry keys:

HKEY_LOCAL_MACHINE\Microsoft\Windows\
CurrentVersion\Run
Windows Defender =

Other Details

This backdoor connects to the following URL(s) to check for an Internet connection:

  • http://google.com
  • http://bing.com
  • http://yahoo.com

It connects to the following possibly malicious URL:

  • {BLOCKED}lrou.com
  • {BLOCKED}xefolgkokdqy.com
  • {BLOCKED}vwvgqlretxd.com
  • {BLOCKED}urhtchwlhwklf.com
  • {BLOCKED}yxjibyd.com
  • {BLOCKED}kbwhfdiufhaj.com
  • {BLOCKED}vxvrq.com
  • {BLOCKED}x.com
  • {BLOCKED}kvn.com
  • {BLOCKED}yyooh.com
  • {BLOCKED}cwgaafbtqkt.com
  • {BLOCKED}olov.com
  • {BLOCKED}ngy.com
  • {BLOCKED}vmhsxtk.com
  • {BLOCKED}slhqyy.com
  • {BLOCKED}dbdkd.com2
  • {BLOCKED}xorlyen.com
  • {BLOCKED}yutodtr.com

  SOLUTION

Minimum Scan Engine:

9.300

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

Scan your computer with your Trend Micro product and note files detected as BKDR_AZBREG.AR

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

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_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    • Micorsoft Windows Service
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root
    • LEGACY_MICORSOFT_WINDOWS_SERVICE

Step 5

Restore this modified 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\SOFTWARE\Microsoft\Security Center
    • From: AntiVirusDisableNotify = "1"
      To: AntiVirusDisableNotify = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Security Center
    • From: FirewallDisableNotify = "1"
      To: FirewallDisableNotify = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Security Center
    • From: UpdatesDisableNotify = "1"
      To: UpdatesDisableNotify = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Security Center
    • From: AntiVirusOverride = "1"
      To: AntiVirusOverride = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Security Center
    • From: FirewallOverride = "1"
      To: FirewallOverride = "0"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\wscsvc
    • From: Start = "4"
      To: Start = "2"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\wuauserv
    • From: Start = "4"
      To: Start = "2"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile
    • From: EnableFirewall = "0"
      To: EnableFirewall = "1"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile
    • From: DisableNotifications = "1"
      To: DisableNotifications = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • From: Userinit = "%System%\userinit.exe,,%Application Data\{random folder name}\{random}.exe"
      To: Userinit = "%System%\userinit.exe,"

Step 6

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\SOFTWARE\Microsoft\Security Center
    • UacDisableNotify = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\system<p align="right"></p>
    • EnableLUA = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {random} = "%Application Data\{random folder name}\{random}.exe"

Step 7

Search and delete this folder

[ 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.
  • %Application Data%\{random folder name}

Step 8

Search and delete this file

[ 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.
  • {All Users' Profile}\Application Data\{random 1}.log
  • %Application Data%\{random 2} .log
  • %Application Data%\{random 3} .log
  • %Application Data%\{random 4}
  • %User Temp%\{random}.sys

Step 9

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


Did this description help? Tell us how we did.