Analysis by: Arianne Grace Dela Cruz
ALIASES:

Trojan:Win32/Casdet!rfn (MICROSOFT); Trojan.PowerShell.Agent.jn (KASPERSKY)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet

This Trojan 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: 312,645 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 21 Nov 2020
Payload: Connects to URLs/IPs

Arrival Details

This Trojan 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 Trojan drops the following files:

  • c:\logdbnnn.txt - serves as infection marker

It adds the following processes:

  • %System%\notepad.exe - 2 instances

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

It injects codes into the following process(es):

  • Spawned %System%\notepad.exe - injects the THANOS Ransomware for execution

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

Other Details

This Trojan does the following:

  • It checks the presence of the following files, and terminates itself if found:
    • c:\logdbnnn.txt
    • c:\logdbnnn.txt.locked
  • It gets the current TCP connections of the machine and enumerates remote IP addresses.
  • It tries to connect to the obtained IP addresses via SMB port 445 and copy itself in the remote machine with the mapped drive X:.
  • Once copied to the remote machine, it will execute the following command:
    • powershell -exec bypass -file %Windows%\{Malware name}.ps1

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 16.364.03
FIRST VSAPI PATTERN DATE: 21 Nov 2020
VSAPI OPR PATTERN File: 16.365.00
VSAPI OPR PATTERN Date: 22 Nov 2020

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

Restart in Safe Mode

[ Learn More ]

Step 4

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.  
  • c:\logdbnnn.txt

Step 5

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Trojan.PS1.LOGDB.YAAK-A. 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.


Did this description help? Tell us how we did.