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BKDR_HELOAG.S

October 09, 2012
 Analysis by: Sabrina Lei Sioting
 ALIASES:

Backdoor:Win32/Heloag.A (Microsoft), Trojan-Downloader.Win32.Agent.esye (Kaspersky), Win32/Heloag.AD (ESET),

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW


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.

  TECHNICAL DETAILS

File Size:

61,440 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

27 Dec 2010

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.

Autostart Technique

This backdoor registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_SSDT_TOOL\
0000
Service = "SSDT_TOOL"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SSDT_TOOL
ImagePath = "\??\{malware path}\SSDT_TOOL.sys"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SSDT_TOOL
DisplayName = "SSDT_TOOL"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SSDT_TOOL\Security
Security = "{hex values}"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SSDT_TOOL\Enum
0 = "Root\LEGACY_SSDT_TOOL\0000"

It registers as a system service to ensure its automatic execution at every system startup by adding the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_SSDT_TOOL

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SSDT_TOOL

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SSDT_TOOL\Security

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SSDT_TOOL\Enum

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://www.{BLOCKED}.com/reques0.asp?kind=020&mac={data}&key={random}

It requires the existence of the following files to properly run:

  • SSDT_TOOL.sys

  SOLUTION

Minimum Scan Engine:

9.200

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Identify and terminate files detected as BKDR_HELOAG.S

[ Learn More ]
  1. 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.
  2. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 3

Delete this registry key

[ 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.

Step 4

Scan your computer with your Trend Micro product to delete files detected as BKDR_HELOAG.S. 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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