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BKDR_SERVU.JBR

April 03, 2013
 Analysis by: Jaime Benigno Reyes
 ALIASES:

Trojan:Win32/Orsam!rts (Microsoft), Server-FTP.Win32.Serv-U.gpr (Kaspersky)

 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: 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 listens on port(s). It executes commands from a remote malicious user, effectively compromising the affected system.

  TECHNICAL DETAILS

File Size:

4,163,072 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

02 Apr 2013

Payload:

Compromises system security

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 component file(s):

  • {malware path}\AvMeter32a.dll - contains the version and process ID of the backdoor
  • {malware path}\pagefile.sys - contains the logs of the backdoor

Backdoor Routine

This backdoor listens on the following port(s):

  • 43958

It executes the following commands from a remote malicious user:

  • Allow anonymous access
  • Execute programs
  • Get information regarding the system
  • List, delete, and create folders
  • Send and receive messages
  • Upload and download files

NOTES:

It is a modified ServU application that may be used as a remote access tool by a remote user. ServU is an FTP server. Using TCP port 43958, it waits for connections from a remote user.

It then allows a remote user to connect to the affected system and perform malicious commands, such as downloading files. The said routine compromises system security.

  SOLUTION

Minimum Scan Engine:

9.300

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_SERVU.JBR

[ 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 these files

[ 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.  
  • {malware path}\AvMeter32a.dll
  • {malware path}\pagefile.sys

Step 4

Scan your computer with your Trend Micro product to delete files detected as BKDR_SERVU.JBR. 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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