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BKDR_COSSTA.BR

January 08, 2016
 PLATFORM:

Windows

 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:

380,928 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

08 Jan 2016

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 creates the following folders:

  • %User Temp%\b

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp 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.)

Other System Modifications

This backdoor deletes the following files:

  • %System Root%\strings.txt
  • %User Temp%\b\strings.txt

(Note: %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.. %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp 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.)

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://www.{BLOCKED}mittelhessen.de/eventbilder/gross/.../strings.txt
  • http://www.{BLOCKED}lm.com.ua/forum/files/.../strings.txt
  • http://www.{BLOCKED}usalumni.net/templates/css/strings.txt
  • http://dasan.{BLOCKED}g.ac.kr/~appmath/test/bbs/strings.txt
  • http://hjca.{BLOCKED}s.gob.ec/{random path}
  • http://{BLOCKED}t.ba/{random path}
  • http://www.{BLOCKED}aslinik.hr/language/de-DE/strings.txt
  • http://www.{BLOCKED}lub.gr/market/oc-includes/json/strings.txt
  • {BLOCKED}.125.108

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.8

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

Search and delete this folder

[ 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.
  • %User Temp%\b

Step 3

Scan your computer with your Trend Micro product to delete files detected as BKDR_COSSTA.BR. 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 4

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%\strings.txt
  • %User Temp%\b\strings.txt


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