Analysis by: Mark Joseph Manahan

ALIASES:

Backdoor:Win32/Kelihos.A (Microsoft), PWS-Zbot.gen.df (McAfee), a variant of Win32/Kryptik.JEF trojan (Eset)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003, Windows Vista, Windows 7

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

This worm may be dropped by other malware.

  TECHNICAL DETAILS

File Size: 461,824 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 27 Dec 2012

Arrival Details

This worm may be dropped by other malware.

Installation

This worm adds the following folders:

  • {All User's Profile}\Application Data\boost_interprocess
  • {All User's Profile}\Application Data\boost_interprocess\{Date and Time of infection}

It adds the following possibly malicious files or file components:

  • {All User's Profile}\Application Data\boost_interprocess\{Date and Time of infection}\GoogleImpl

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
SmartIndex = "{malware path and file name}"

Other System Modifications

This worm adds the following registry keys:

HKEY_CURRENT_USER\Software\Google

It adds the following registry entries:

HKEY_CURRENT_USER\Software\Google
ID = "50"

HKEY_CURRENT_USER\Software\Google
ID2 = "{random values}"

HKEY_CURRENT_USER\Software\Google
ID3 = "{random values}"

HKEY_CURRENT_USER\Software\Google
AppID = "{random characters}"

It creates the following registry entry(ies) to bypass Windows Firewall:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
{Malware Path and Filename} = "{Malware Path and Filename}:*:Enabled:{Filename}"

Other Details

This worm connects to the following possibly malicious URL:

  • http://{BLOCKED}.{BLOCKED}.185.46/vYho/w5/pMSeoeJQF.htm

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 9.620.05
FIRST VSAPI PATTERN DATE: 27 Dec 2012
VSAPI OPR PATTERN File: 9.621.00

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

Identify and terminate files detected as WORM_KELIHOS.MT

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. 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.
  3. 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 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.

  • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
  • SmartIndex = "{malware path and file name}"
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
  • {Malware Path and Filename} = "{Malware Path and Filename}:*:Enabled:{Filename}"

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_CURRENT_USER\Software
    • Google

Step 5

Search and delete this folder

[ 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.  
  • {All User's Profile}\Application Data\boost_interprocess

Step 6

Scan your computer with your Trend Micro product to delete files detected as WORM_KELIHOS.MT. 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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