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BKDR_CRUGUP.AD

July 03, 2015
 Analysis by: David John Agni
 ALIASES:

Win32/Pliskal.A (ESET-NOD32), W32/Pliskal.A!tr (Fortinet), Trojan.Win32.Reconyc.ehmt (Kaspersky), Backdoor:Win32/Crugup.A (Microsoft)

 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 commands from a remote malicious user, effectively compromising the affected system. It connects to a website to send and receive information.

It sends the information it gathers to remote users via HTTP Post.

  TECHNICAL DETAILS

File Size:

173,401 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

23 Jun 2015

Payload:

Connects to URLs/IPs

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 and executes them:

  • %Application Data%\{Folder Name}\svchost.exe

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming 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 creates the following folders:

  • %Application Data%\{Folder Name}

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming 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 adds the following mutexes to ensure that only one of its copies runs at any one time:

  • GH5K-GKL8-CPP4-DE24

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\Run
z64_kernel = %Application Data%\{Folder Name}\svchost.exe

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
z64_kernel = %Application Data%\{Folder Name}\svchost.exe

Other System Modifications

This backdoor also creates the following registry entry(ies) as part of its installation routine:

HKEY_CURRENT_USER\Software\cppguru
mv = "Mi4wNQ==" -> base64 encoded version = 2.05

It creates the following registry entry(ies) to bypass Windows Firewall:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\SharedAccess\Parameters\
FirewallPolicy\FirewallRules
{GUID} = "v{version number}|Action=Allow|Active=TRUE|Dir=In|App=%Application Data%\{Folder Name}\svchost.exe|Name=madservice|"

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

  • Download and execute file
  • Use Internet Explorer to connect remote sites
  • Update itself
  • Delete itself
  • Perform denial of service attacks

It connects to the following websites to send and receive information:

  • http://{BLOCKED}otkill.ru/mad/index.php

As of this writing, the said sites are inaccessible.

Download Routine

This backdoor saves the files it downloads using the following names:

  • -%Application Data%\sqlite3.dll
  • -%Application Data%\WinXP.exe

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming 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.)

Information Theft

This backdoor gathers the following data:

  • Volume serial number
  • OS version
  • If the machine is running with administrative privileges

Drop Points

This backdoor sends the information it gathers to remote users via HTTP Post.

NOTES:

{Folder Name} in the registry entries refers to {First 8 digits of the Volume Serial Number}.

It uses the following User Agents:

  • Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.0.5) Gecko/20060731 Firefox/1.5.0.5 Flock/0.7.4.1
  • Mozilla/5.0 (X11; U; Linux 2.4.2-2 i586; en-US; m18) Gecko/20010131 Netscape6/6.01
  • Mozilla/5.0 (compatible; MSIE 8.0; Windows NT 6.2; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0)
  • Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.2; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0)
  • Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:0.9.6) Gecko/20011128
  • Mozilla/4.0 (MobilePhone SCP-5500/US/1.0) NetFront/3.0 MMP/2.0 (compatible; Googlebot/2.1; http://www.google.com/bot.html)
  • Mozilla/4.0 (Windows; U; Windows NT 6.1; nl; rv:1.9.2.3) Gecko/20100401 Firefox/3.6.3
  • Mozilla/4.0 (Windows NT 5.1; U; en) Presto/2.5.22 Version/10.50
  • Mozilla/4.0 Galeon/1.2.0 (X11; Linux i686; U;) Gecko/20020326
  • Opera/10.80 (SunOS 5.8 sun4u; U) Opera 10.8 [en]

It restarts the affected system if it ables to find the following file:

  • ollydbg.ini
  • symsrv.dll
  • SDRemote.dll
  • icedat.dll
  • nmtrans.dll
  • srcsrv.dll
  • symsrv.dll
  • ImmunityDebugger.ini
  • ida.key
  • libdwarf.dll

It creates the following files:

  • {malware path}\per – contains the following string deleted after use.
  • {registry key} [7] - to make the registry key Full Access permission
  • {malware path}\perper – contains the following string deleted after use.
  • {registry key} [8] - to make the registry key Read Access permission
  • where {registry key} can be one of the following:
  • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
  • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

It executes the following command to change the registry access permission:

regini {one of the created files in the list above}

It prevents the manual removal of the dropped copy of itself by executing the following command to change the permission to read or execute:

  • CACLS "%Application Data%\{8 random number}\svchost.exe" /P "{Host Name}:R"

  SOLUTION

Minimum Scan Engine:

9.750

FIRST VSAPI PATTERN FILE:

11.748.01

FIRST VSAPI PATTERN DATE:

23 Jun 2015

VSAPI OPR PATTERN File:

11.749.00

VSAPI OPR PATTERN Date:

24 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

Identify and terminate files detected as BKDR_CRUGUP.AD

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • z64_kernel = %Application Data%\{8 random number}\svchost.exe
  • In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • z64_kernel = %Application Data%\{8 random number}\svchost.exe
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\SharedAccess\Parameters\FirewallPolicy\FirewallRules
    • {GUID} = "v{version number}|Action=Allow|Active=TRUE|Dir=In|App=%Application Data%\{Folder Name}\svchost.exe|Name=madservice|"

Step 5

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
    • cppguru

Step 6

Scan your computer with your Trend Micro product to delete files detected as BKDR_CRUGUP.AD. 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

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.
  • %Application Data%\{Folder Name}


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