BKDR_ANDROM.YUYDA

June 17, 2015
 Analysis by: Francis Xavier Antazo
 ALIASES:

Worm:Win32/Gamarue (Microsoft); Backdoor.Trojan(Symantec); Backdoor.Win32.Androm.hbck(Kaspersky)

 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware

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 executes then deletes itself afterward.

However, as of this writing, the said sites are inaccessible.

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size:

74,240 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

05 Jun 2015

Payload:

Compromises system security, Connects to URLs/IPs, Steals information

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:

  • %All Users Profile%\ms{random}.exe

(Note: %All Users Profile% is the All Users folder, where it usually is C:\Documents and Settings\All Users on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData 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.)

It executes then deletes itself afterward.

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run
{random number} = "%All Users Profile%\ms{random}.exe"

Other System Modifications

This backdoor adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
TaskbarNoNotification = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
HideSCAHealth = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer
TaskbarNoNotification = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer
HideSCAHealth = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
system
EnableLUA = "0"

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CurrentVersion\Windows
Load = ""

It modifies the following registry entries:

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
Start = "4"

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

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

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

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

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
Hidden = "2"

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
ShowSuperHidden = "0"

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

Backdoor Routine

However, as of this writing, the said sites are inaccessible.

Other Details

This backdoor connects to the following possibly malicious URL:

  • {BLOCKED}8888-3.eu

It deletes the initially executed copy of itself

  SOLUTION

Minimum Scan Engine:

9.750

FIRST VSAPI PATTERN FILE:

11.712.06

FIRST VSAPI PATTERN DATE:

01 Jun 2015

VSAPI OPR PATTERN File:

11.713.00

VSAPI OPR PATTERN Date:

02 Jun 2015

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

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 3

Restart in Safe Mode

[ Learn More ]

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\Policies\Explorer
    • TaskbarNoNotification = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
    • HideSCAHealth = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer
    • TaskbarNoNotification = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer
    • HideSCAHealth = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\system
    • EnableLUA = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows
    • Load = ""

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: Hidden = "2"
      To: Hidden = 1
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: ShowSuperHidden = "0"
      To: ShowSuperHidden = 1
  • 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
    • From: Start = "4"
      To: Start = 2
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MpsSvc
    • From: Start = "4"
      To: Start = 2
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WinDefend
    • From: Start = "4"
      To: Start = 2

Step 6

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