ALIASES:

Trojan:Win32/Lethic.B (Microsoft); RDN/Generic BackDoor!zd (McAfee); Trojan.Gen (Symantec); Backdoor.Win32.Azbreg.aahc (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt); Trojan horse Inject2.AOCO (AVG)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

 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.

  TECHNICAL DETAILS

File Size: 141,824 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 06 Aug 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 drops the following copies of itself into the affected system:

  • %System Root%\RECYCLER\S-1-5-21-0243556031-888888379-781863308-6105641\zy66864n6.exe

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

It creates the following folders:

  • %System Root%\RECYCLER
  • %System Root%\RECYCLER\S-1-5-21-0243556031-888888379-781863308-6105641

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Taskman = "%System Root%\RECYCLER\S-1-5-21-0243556031-888888379-781863308-6105641\zy66864n6.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
zy866in6 = "%System Root%\RECYCLER\S-1-5-21-0243556031-888888379-781863308-6105641\zy66864n6.exe"

Other System Modifications

This backdoor deletes the following files:

  • %System Root%\RECYCLER\S-1-5-21-0243556031-888888379-781863308-6105641\zy66864n6.exe

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

It adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CurrentVersion\Winlogon
Shell = "{random characters}"

Dropping Routine

This backdoor drops the following files:

  • %System Root%\RECYCLER\S-1-5-21-0243556031-888888379-781863308-6105641\Desktop.ini

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

Other Details

This backdoor connects to the following possibly malicious URL:

  • {BLOCKED}6.90.92
  • {BLOCKED}9.194.234

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

Identify and delete files detected as BKDR_AZBREG.BD using either the Startup Disk or Recovery Console

[ Learn More ]

Step 3

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\Windows NT\CurrentVersion\Winlogon
    • Taskman = "%System Root%\RECYCLER\S-1-5-21-0243556031-888888379-781863308-6105641\zy66864n6.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • zy866in6 = "%System Root%\RECYCLER\S-1-5-21-0243556031-888888379-781863308-6105641\zy66864n6.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Winlogon
    • Shell = "{random characters}"

Step 4

Search and delete this file

[ Learn More ]
There may be some 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.
  • %System Root%\RECYCLER\S-1-5-21-0243556031-888888379-781863308-6105641\Desktop.ini

Step 5

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.
  • %System Root%\RECYCLER
  • %System Root%\RECYCLER\S-1-5-21-0243556031-888888379-781863308-6105641

Step 6

Scan your computer with your Trend Micro product to delete files detected as BKDR_AZBREG.BD. 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.

Step 7

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

  • %System Root%\RECYCLER\S-1-5-21-0243556031-888888379-781863308-6105641\zy66864n6.exe


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