Trojan.PS1.KILLAV.AA

March 11, 2021
 Analysis by: Denisse Camille Layco
 ALIASES:

N/A

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware

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.

It does not have any propagation routine.

It does not have any backdoor routine.

  TECHNICAL DETAILS

File Size:

3,074 bytes

File Type:

PS1

Memory Resident:

No

Initial Samples Received Date:

05 Mar 2021

Payload:

Drops files, Terminates processes

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:

  • \\{BLOCKED}.{BLOCKED}.local\log${Computer Name}.txt

It adds the following processes:

  • cmd.exe /c 'C:\Program Files\Malwarebytes\Anti-Malware\unins001.exe' /silent /noreboot
  • 'C:\Program Files\Malwarebytes\Anti-Malware\unins000.exe' /silent /noreboot
  • "C:\Program Files\Microsoft Security Client\Setup.exe" /x /s
  • dism /online /Disable-Feature /FeatureName:Windows-Defender /Remove /NoRestart /quiet
  • vssadmin delete shadows /all /quiet
  • wbadmin stop job
  • cmd.exe /c assoc .README=txtfile

Other System Modifications

This Trojan modifies the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Control\Terminal Server
fDenyTSConnections = 0

(Note: The default value data of the said registry entry is 1.)

Propagation

This Trojan does not have any propagation routine.

Backdoor Routine

This Trojan does not have any backdoor routine.

Rootkit Capabilities

This Trojan does not have rootkit capabilities.

Process Termination

This Trojan terminates processes or services that contain any of the following strings if found running in the affected system's memory:

  • Stop and disable services with the following strings in their name:
    • SQL
    • Oracle
    • Citrix
    • Exchange
    • Veeam
    • Malwarebytes
    • Sharepoint
    • Quest
    • Backup
  • Terminates processes using the following commands:
    • wmic process where "name like '%{string}%'" delete
  • Process strings:
    • Agent
    • Malware
    • Endpoint
    • Citrix
    • sql
    • Veeam
    • Core.Service
    • Mongo
    • Backup
    • QuickBooks
    • QBDB
    • QBData
    • QBCF
    • server
    • sage
    • http
    • apache
    • web
    • vnc
    • teamviewer
    • OCS Inventory
    • monitor
    • security
    • def
    • dev
    • office
    • anydesk
    • protect
    • secure
    • segurda
    • center
    • silverlight
    • exchange
    • manage
    • acronis
    • autodesk
    • database
    • adobe
    • java
    • logmein
    • microsoft
    • solarwinds
    • engine
    • AlwaysOn
    • Framework
    • sprout
    • firefox
    • chrome
    • barracuda
    • arcserve

Other Details

This Trojan does the following:

  • Uninstalls MalwareBytes Anti-Malware
  • Disables Real-time monitoring for Windows Defender
  • Excludes .exe files from scans
  • Deletes computer restore points
  • Uninstalls Windows Defender and removes its installation package
  • Deletes shadow copies
  • Cancels backup or recovery operation
  • It performs UDP broadcast to the following IP address:
    • 255.255.255.255
  • Enables remote desktop connection
  • Change local users' passwords

It does not exploit any vulnerability.

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

16.576.04

FIRST VSAPI PATTERN DATE:

05 Mar 2021

VSAPI OPR PATTERN File:

16.577.00

VSAPI OPR PATTERN Date:

06 Mar 2021

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 Trojan.PS1.KILLAV.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

Restore this modified registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Terminal Server
    • From: fDenyTSConnections = 0
      To: fDenyTSConnections = 1

Step 5

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.
  • \\{BLOCKED}.{BLOCKED}.local\log${Computer Name}.txt

Step 6

Scan your computer with your Trend Micro product to delete files detected as Trojan.PS1.KILLAV.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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