Analysis by: Neljorn Nathaniel Aguas
ALIASES:

Backdoor:ASP/Webshell.Y (MICROSOFT)

 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • 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 runs certain commands that it receives remotely from a malicious user. Doing this puts the affected computer and information found on the computer at greater risk.

It does not have any information-stealing capability.

  TECHNICAL DETAILS

File Size: 4,546 bytes
File Type: ASP
Memory Resident: No
Initial Samples Received Date: 13 Feb 2024
Payload: Executes commands

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.

Propagation

This Backdoor does not have any propagation routine.

Backdoor Routine

This Backdoor executes the following command(s) from a remote malicious user:

  • Execute arbitrary C# codes.

Rootkit Capabilities

This Backdoor does not have rootkit capabilities.

Information Theft

This Backdoor does not have any information-stealing capability.

Other Details

This Backdoor does the following:

  • It receives C# codes and stores in the variable "p1" using form parameters then compiled and executed on the compromised web server where it is hosted.

It does not exploit any vulnerability.

It requires being hosted on a web server in order to proceed with its intended routine.

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 19.156.04
FIRST VSAPI PATTERN DATE: 13 Feb 2024
VSAPI OPR PATTERN File: 19.157.00
VSAPI OPR PATTERN Date: 14 Feb 2024

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

Scan your computer with your Trend Micro product to delete files detected as Backdoor.ASP.WEBSHELL.D. 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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