BKDR_SMALL.LEC

October 08, 2012
 Analysis by: Jeffrey Bernardino
 PLATFORM:

Windows 2000, XP, Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

This {insert malware/spyware type} uses social engineering methods to lure users into performing certain actions that may, directly or indirectly, cause malicious routines to be performed. Specifically, it uses Trend Micro to lure users that the package came from a real antivirus company.

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

This backdoor may be dropped by other malware.

It executes commands from a remote malicious user, effectively compromising the affected system.

  TECHNICAL DETAILS

Ports:

TCP Port 443

File Size:

Varies

File Type:

PE

Memory Resident:

Yes

Initial Samples Received Date:

03 Sep 2010

Arrival Details

This backdoor may be dropped by the following malware:

  • TROJ_DROPPER.JAS

Installation

This backdoor is injected into the following processes running in memory:

  • SVCHOST.EXE

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\
Services\Ias\Parameters
ServiceDll = "%System%\Iasex.dll"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Nwsapagent\Parameters
ServiceDll = "%System%\Nwsapagentex.dll"

Backdoor Routine

This backdoor opens the following port(s) where it listens for remote commands:

  • TCP port 443

It executes the following commands from a remote malicious user:

  • Capture screen shots
  • Clear event logs
  • Copy data from clipboard
  • Enumerate files on local drives
  • Log keystrokes
  • Start and stop certain services

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

  • {BLOCKED}.{BLOCKED}.84.234
  • {BLOCKED}.{BLOCKED}.174.135
  • {BLOCKED}w.{BLOCKED}ecs.com.tw
  • {BLOCKED}y.{BLOCKED}ecs.com.tw
  • {BLOCKED}r.{BLOCKED}ecs.com.tw

  SOLUTION

Minimum Scan Engine:

8.900

FIRST VSAPI PATTERN FILE:

7.428.09

FIRST VSAPI PATTERN DATE:

01 Sep 2010

VSAPI OPR PATTERN File:

7.429.00

VSAPI OPR PATTERN Date:

01 Sep 2010

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

Remove malware files dropped/downloaded by BKDR_SMALL.LEC

    • TROJ_DROPPER.JAS

Step 3

Identify and delete files detected as BKDR_SMALL.LEC using the Recovery Console

[ Learn More ]

Step 4

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.

  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\
    • Ias
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\
    • Nwsapagent

Step 5

Scan your computer with your Trend Micro product to delete files detected as BKDR_SMALL.LEC. 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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