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Threat Encyclopedia

WORM_ROMBRAST.AD

ANALYSIS BY

Mark Joseph Manahan


ALIASES:

Win32/AutoRun.Agent.AGC worm (Eset), W32/Autorun.worm.c (McAfee), Worm:Win32/Rombrast (Microsoft),

PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type:Worm

  • Destructiveness:No

  • Encrypted: Yes

  • In the wild: Yes

OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware, Propagates via removable drives


This worm is an emerging toolkit seen in the black market. It has the potential to be the next hot botnet malware, similar to DORKBOT.

To get a one-glance comprehensive view of the behavior of this Worm, refer to the Threat Diagram shown below.

This worm arrives via removable drives. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It is injected into all running processes to remain memory resident.

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

It executes commands from a remote malicious user, effectively compromising the affected system. It connects to a website to send and receive information.

It also has rootkit capabilities, which enables it to hide its processes and files from the user.

TECHNICAL DETAILS

File Size:

81,920 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

03 Dec 2012

Payload:

Compromises system security, Connects to URLs/IPs, Drops files

Arrival Details

This worm arrives via removable drives.

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

  • %Application Data%\{random}\{random}.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 and 7.)

It drops the following files:

  • %Application Data%\{random}\{random}.log
  • %Application Data%\{random}\{random}.cfg

(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 and 7.)

It creates the following folders:

  • %Application Data%\{random}

(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 and 7.)

It is injected into all running processes to remain memory resident.

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
{random} = "%Application Data%\{random}\{random},exe"

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
{random} = "%Application Data%\{random}\{random},exe"

Propagation

This worm drops the following copy(ies) of itself in all removable drives:

  • {random}_l.exe
  • {random}_a.exe

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

The said .INF file contains the following strings:

[autorun]
open={random}_a.exe

Backdoor Routine

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

  • Visit URL
  • Form Grabber (Chrome, IExplore, Firefox)
  • UDP / SYN / Slowloris Flooding
  • Download and execute arbitrary files
  • Update / Uninstall itself
  • DNS Hook
  • FTP Grabber

It connects to the following websites to send and receive information:

  • {pseudorandom}.{BLOCKED}chsecurity.biz
  • {pseudorandom}.{BLOCKED}tversion1.biz
  • {pseudorandom}.{BLOCKED}x.biz

Rootkit Capabilities

This worm also has rootkit capabilities, which enables it to hide its processes and files from the user.

NOTES:

This worm drops the following shortcut link in removable drives to load the malware using folder names found on the device:

  • {drive letter}:\{folder name}.lnk - detected as LNK_JORIK.SMC

SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

9.568.05

FIRST VSAPI PATTERN DATE:

03 Dec 2012

VSAPI OPR PATTERN File:

9.569.00

VSAPI OPR PATTERN Date:

04 Dec 2012

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

Remove the malware/grayware file dropped/downloaded by WORM_ROMBRAST.AD

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

Scan your computer with your Trend Micro product and note files detected as WORM_ROMBRAST.AD

Step 5

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • {random} = "%Application Data%\{random}\{random},exe"
  • In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • {random} = "%Application Data%\{random}\{random},exe"

Step 6

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%\{random}

Step 7

Search and delete AUTORUN.INF files created by WORM_ROMBRAST.AD that contain these strings

[ Learn More ]
[autorun]
open={random}_a.exe

Step 8

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