Analysis by: Augusto II Remillano
ALIASES:

HEUR:Trojan-Spy.Win32.Agent.gen (Kaspersky)

 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • 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 executes commands from a remote malicious user, effectively compromising the affected system. However, as of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size: 733,184 bytes
File Type: EXE
File Compression: Delphi
Memory Resident: Yes
Initial Samples Received Date: 31 Aug 2018
Payload: Drops files, Steals information, Compromises system security

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 drops the following copies of itself into the affected system and executes them:

  • %Application Data%\Install\Hostaug.exe

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, and 8.)

It creates the following folders:

  • %Application Data%\Install
  • %Application Data%\Logs

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, and 8.)

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

  • SYwjjqxx

Autostart Technique

This Backdoor adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Netaugust = "%Application Data%\Install\Hostaug.exe"

Backdoor Routine

This Backdoor executes the following commands from a remote malicious user:

  • Execute command shell
  • list files on a directory
  • terminate processes
  • perform keylogging routine

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • ddns.{BLOCKED}sky.biz:4488

However, as of this writing, the said sites are inaccessible.

Dropping Routine

This Backdoor drops the following file(s), which it uses for its keylogging routine:

  • %Application Data%\Logs\{DD-MM-YYYY}

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, and 8.)

Information Theft

This Backdoor attempts to steal stored email credentials from the following:

  • Windows Live Mail
  • Microsoft Outlook

It attempts to get stored information such as user names, passwords, and hostnames from the following browsers:

  • Mozilla Firefox
  • Mozilla Thunderbird
  • Mozilla SeaMonkey
  • Internet Explorer
  • Google Chrome

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 14.484.04
FIRST VSAPI PATTERN DATE: 04 Sep 2018
VSAPI OPR PATTERN File: 14.485.00
VSAPI OPR PATTERN Date: 05 Sep 2018

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

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

Delete this 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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Netaugust = "%Application Data%\Install\Hostaug.exe"

Step 5

Search and delete these folders

[ 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.
  • %Application Data%\Install
  • %Application Data%\Logs

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_NETWIRED.TIGBOAK. 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.


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