Analysis by: Carl Maverick Pascual
ALIASES:

Backdoor:Win32/Tapazom.A (Microsoft); a variant of Win32/Delf.OHC trojan (Nod32)

 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • 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 does not have any propagation routine.

It executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system. As of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size: 30,208 bytes
File Type: EXE
Initial Samples Received Date: 16 Aug 2019
Payload: Connects to URLs/IPs, Downloads files

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 adds the following mutexes to ensure that only one of its copies runs at any one time:

  • decomcs64.dll

Propagation

This Backdoor does not have any propagation routine.

Download Routine

This Backdoor connects to the following URL(s) to download its component file(s):

  • mzo.{BLOCKED}.org:1431

It saves the files it downloads using the following names:

  • {malware path}\decomcs64.dll

It then executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

As of this writing, the said sites are inaccessible.

Other Details

This Backdoor does the following:

  • It sends the following request format:
    • GETSERVER|111|46
  • The downloaded DLL is executed in-memory, which should perform the backdoor capabilities

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 15.306.02
FIRST VSAPI PATTERN DATE: 18 Aug 2019
VSAPI OPR PATTERN File: 15.307.00
VSAPI OPR PATTERN Date: 19 Aug 2019

Step 1

Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 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 Backdoor.Win32.TAPAZOM.AA

[ 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

Scan your computer with your Trend Micro product to delete files detected as Backdoor.Win32.TAPAZOM.AA. 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 the following Trend Micro Support pages for more information:


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