BKDR_FULAIRO.SM

June 09, 2014
 Analysis by: Odessy Silva
 ALIASES:

Trojan:Win32/Cueisfry.A (Microsoft)

 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:
 INFORMATION EXPOSURE:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • 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.

  TECHNICAL DETAILS

File Size:

Varies

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

20 Jan 2014

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.

Autostart Technique

This backdoor drops the following shortcut pointing to its copy in the User Startup folder to enable its automatic execution at every system startup:

  • AntiVir_Update.url

Backdoor Routine

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

  • It receives a shell command from http://{CnC Server}/{varies}/com.php and performs it using shell execute.
  • The output result will be saved as %User Temp%\~AC43E.tmp and will be sent via http as http://{CnC Server}/{varies}/info.php?Re={output result}. %User Temp%\~AC43E.tmp will be deleted afterwards.

(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, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • http://{BLOCKED}.{BLOCKED}.114.231/
  • http://{BLOCKED}.{BLOCKED}.3.152
  • http://{BLOCKED}.{BLOCKED}.162.223
  • http://{BLOCKED}.{BLOCKED}.234.41/

Download Routine

This backdoor accesses the following websites to download files:

  • http://{C&C Server}/{Varies}/update.html

It saves the files it downloads using the following names:

  • %User Temp%\~WDA4581A.tmp

(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, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

Information Theft

This backdoor gathers the following data:

  • list of running processes

Stolen Information

This backdoor saves the stolen information in the following file:

  • %User Temp%\~Pro75C.DAT

(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, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

It sends the gathered information via HTTP POST to the following URL:

  • http://{C&C server}/{varies}/info.php?secue={status}&pro={logged info(running processes)}

NOTES:

It checks first if the file to be downloaded exists in %User Startup%. If not, it will download the file from http://{C&C Server}/{Varies}/update.html and saves it as %User Temp%\~WD4581A.tmp. The downloaded %User Temp%\~WDA4581A.tmp will be copied to the %User Startup%. Then, %User Temp%\~WDA4581A.tmp will be deleted.

{C&C Server} is any of the following:

  • http://{BLOCKED}.{BLOCKED}.114.231
  • http://{BLOCKED}.{BLOCKED}.234.41
  • http://{BLOCKED}.{BLOCKED}.3.152
  • http://{BLOCKED}.{BLOCKED}.162.223

  SOLUTION

Minimum Scan Engine:

9.700

VSAPI OPR PATTERN File:

10.805.00

VSAPI OPR PATTERN Date:

19 May 2014

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 terminate files detected as BKDR_FULAIRO.SM

[ 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 3

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.
  • %User Temp%\~Pro75C.DAT
  • %User Startup%\AntiVir_Update.url

Step 4

Scan your computer with your Trend Micro product to delete files detected as BKDR_FULAIRO.SM. 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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