Analysis by: Rhena Inocencio
ALIASES:

Mal/Packer (Sophos) ,W32/Heuristic-210!Eldorado (damaged, not disinfectable) (Fprot) ,Trojan.SuspectCRC (Ikarus) ,HEUR:Trojan.Win32.Generic (Kaspersky) ,Backdoor:Win32/Zegost.AY (Microsoft) ,Backdoor.Trojan (Symantec) ,Trojan.Win32.Generic!BT (Sunbelt)

 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:
 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 connects to a website to send and receive information.

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size: 332,873 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 20 May 2014
Payload: Compromises system security, Collects system information, Terminates processes

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 adds the following possibly malicious files or file components:

  • %System Root%\{random foldername}\{random filename}.dll - detected as BKDR_ZEGOST.TPAN
  • %System Root%\{random foldername}\MUpdate.exe

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

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
CTFM0N = "%System Root%\{random foldername}\MUpdate.exe "%System Root%\{random foldername}\{random filename}.dll,ALSTS_ExecuteAction""

Backdoor Routine

This backdoor connects to the following websites to send and receive information:

  • {BLOCKED}.{BLOCKED}.119.178
  • {BLOCKED}.{BLOCKED}ION.INFO
  • {BLOCKED}0.{BLOCKED}s.info
  • v.{BLOCKED}n.com

As of this writing, the said servers are currently inaccessible.

HOSTS File Modification

This backdoor modifies the system's HOSTS files to redirect users once the following Web site(s) are accessed:

  • 126.117.125.213 nAVER.coM
  • 126.117.125.213 kIsA.hoNabenk.coM
  • 126.117.125.213 kIsA.kcB.co.kR
  • 126.117.125.213 kIsA.kfoc.co.kR
  • 126.117.125.213 www.nAVER.co.KR
  • 126.117.125.213 nAVER.cO.kR
  • 126.117.125.213 www.nONGhyup.coM
  • 126.117.125.213 BaNKiNg.nONGhyup.coM
  • 126.117.125.213 iBz.nONGhyup.coM
  • 126.117.125.213 www.nAVER.coM
  • 126.117.125.213 nAVER.kR
  • 126.117.125.213 www.nAVER.Kr
  • 126.117.125.213 KisA.kBstor.coM
  • 126.117.125.213 KisA.nONGhuyp.coM
  • 126.117.125.213 KisA.nONGhyup.coM
  • 126.117.125.213 KisA.shiNhoN.coM
  • 126.117.125.213 KisA.WOORibenk.coM
  • 126.117.125.213 KisA.IDK.co.kR
  • 126.117.125.213 KisA.ibek.co.kR
  • 126.117.125.213 KisA.EPostbenk.go.kR
  • 126.117.125.213 KisA.hanAbenk.coM
  • 126.117.125.213 KisA.keB.co.kR
  • 126.117.125.213 KisA.kcB.co.kR
  • 126.117.125.213 KisA.kfoc.co.kR
  • 126.117.125.213 KisA.kfcc.co.kR
  • 126.117.125.213 www.nATe.nEt
  • 126.117.125.213 kIsA.kBstor.coM
  • 126.117.125.213 kIsA.hanabank.com
  • 126.117.125.213 kIsA.Nenghuyp.coM
  • 126.117.125.213 kIsA.shiNhoN.coM
  • 126.117.125.213 kIsA.wooribenk.coM
  • 126.117.125.213 kIsA.idk.co.kR
  • 126.117.125.213 kIsA.epostbenk.go.kR
  • 126.117.125.213 kIsA.hoNabenk.coM
  • 126.117.125.213 kIsA.kcB.co.kR
  • 126.117.125.213 kIsA.kfoc.co.kR
  • 126.117.125.213 KisA.kBstAR.coM
  • 126.117.125.213 www.nATe.Kr
  • 126.117.125.213 nATe.kR
  • 126.117.125.213 phARmiNg.KisA.or.kR
  • 126.117.125.213 www.GmARkeT.cO.kr
  • 126.117.125.213 BizBaNk.shiNhaN.coM
  • 126.117.125.213 oPEN.shiNhaN.coM
  • 126.117.125.213 daUm.NeT
  • 126.117.125.213 gMARkEt.CO.kr
  • 126.117.125.213 www.nATe.cO.kr
  • 126.117.125.213 nATe.Co.Kr
  • 126.117.125.213 myBaNk.iBk.co.kR
  • 126.117.125.213 Kiup.iBk.co.kR
  • 126.117.125.213 oPEN.iBk.co.kR
  • 126.117.125.213 www.daum.NeT
  • 126.117.125.213 WOORiBaNk.coM
  • 126.117.125.213 haNmail.NeT
  • 126.117.125.213 eBaNk.keB.co.kR
  • 126.117.125.213 www.gmARket.co.kr
  • 126.117.125.213 oNliNe.keB.co.kR
  • 126.117.125.213 oPEN.keB.co.kR
  • 126.117.125.213 www.haNmail.Net
  • 126.117.125.213 oPEN.hanABaNk.com
  • 126.117.125.213 www.hanAcBs.coM
  • 126.117.125.213 kfCc.co.kR
  • 126.117.125.213 www.kfcc.co.kR
  • 126.117.125.213 iBs.kfcc.co.kR
  • 126.117.125.213 EPostBaNk.go.kR
  • 126.117.125.213 www.EPostBaNk.go.kR
  • 126.117.125.213 www.nAte.com

Information Theft

This backdoor gathers the following data:

  • OS version
  • System's default language
  • Processor information

Other Details

This backdoor drops the following file(s)/component(s):

  • %System%\drivers\etc\hosts.ics - temporary file that contains contents of data.mdb
  • {malware path}\data.mdb - contains the decrypted received data. This is deleted after contents are copied to the hosts file

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

It deletes the initially executed copy of itself

NOTES:

It accesses the following sites to download encrypted data:

  • http://{BLOCKED}.{BLOCKED}.241.109:805/plus.php

The encrypted data contains the list of sites that will be added to the HOSTS file.

It queries the following registry key to get the processor information:

  • HKEY_LOCAL_MACHINE\HARDWARE\DESCRIPTION\System\CentralProcessor\0\~MHz

It attempts to terminate the following processes:

  • ASDSvc.exe
  • AYRTSrv.aye

  SOLUTION

Minimum Scan Engine: 9.700
FIRST VSAPI PATTERN FILE: 10.806.04
FIRST VSAPI PATTERN DATE: 20 May 2014
VSAPI OPR PATTERN File: 10.807.00
VSAPI OPR PATTERN Date: 21 May 2014

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

Scan your computer with your Trend Micro product and note files detected as BKDR_ZEGOST.TPAN

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
    • CTFM0N = "%System Root%\{random foldername}\MUpdate.exe "%System Root%\{random foldername}\{random filename}.dll,ALSTS_ExecuteAction""

Step 5

Search and delete these files

[ Learn More ]
There may be some component files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden files and folders in the search result.  
  • %System Root%\{random foldername}\{random filename}.dll
  • %System Root%\{random foldername}\MUpdate.exe

Step 6

Remove these strings added by the malware/grayware/spyware in the HOSTS file

[ Learn More ]
     
    • 126.117.125.213  nAVER.coM
    • 126.117.125.213  kIsA.hoNabenk.coM
    • 126.117.125.213  kIsA.kcB.co.kR
    • 126.117.125.213  kIsA.kfoc.co.kR
    • 126.117.125.213  www.nAVER.co.KR
    • 126.117.125.213  nAVER.cO.kR
    • 126.117.125.213  www.nONGhyup.coM
    • 126.117.125.213  BaNKiNg.nONGhyup.coM
    • 126.117.125.213  iBz.nONGhyup.coM
    • 126.117.125.213  www.nAVER.coM
    • 126.117.125.213  nAVER.kR
    • 126.117.125.213  www.nAVER.Kr
    • 126.117.125.213  KisA.kBstor.coM
    • 126.117.125.213  KisA.nONGhuyp.coM
    • 126.117.125.213  KisA.nONGhyup.coM
    • 126.117.125.213  KisA.shiNhoN.coM
    • 126.117.125.213  KisA.WOORibenk.coM
    • 126.117.125.213  KisA.IDK.co.kR
    • 126.117.125.213  KisA.ibek.co.kR
    • 126.117.125.213  KisA.EPostbenk.go.kR
    • 126.117.125.213  KisA.hanAbenk.coM
    • 126.117.125.213  KisA.keB.co.kR
    • 126.117.125.213  KisA.kcB.co.kR
    • 126.117.125.213  KisA.kfoc.co.kR
    • 126.117.125.213  KisA.kfcc.co.kR
    • 126.117.125.213  www.nATe.nEt
    • 126.117.125.213  kIsA.kBstor.coM
    • 126.117.125.213  kIsA.hanabank.com
    • 126.117.125.213  kIsA.Nenghuyp.coM
    • 126.117.125.213  kIsA.shiNhoN.coM
    • 126.117.125.213  kIsA.wooribenk.coM
    • 126.117.125.213  kIsA.idk.co.kR
    • 126.117.125.213  kIsA.epostbenk.go.kR
    • 126.117.125.213  kIsA.hoNabenk.coM
    • 126.117.125.213  kIsA.kcB.co.kR
    • 126.117.125.213  kIsA.kfoc.co.kR
    • 126.117.125.213  KisA.kBstAR.coM
    • 126.117.125.213  www.nATe.Kr
    • 126.117.125.213  nATe.kR
    • 126.117.125.213  phARmiNg.KisA.or.kR
    • 126.117.125.213  www.GmARkeT.cO.kr
    • 126.117.125.213  BizBaNk.shiNhaN.coM
    • 126.117.125.213  oPEN.shiNhaN.coM
    • 126.117.125.213  daUm.NeT
    • 126.117.125.213  gMARkEt.CO.kr
    • 126.117.125.213  www.nATe.cO.kr
    • 126.117.125.213  nATe.Co.Kr
    • 126.117.125.213  myBaNk.iBk.co.kR
    • 126.117.125.213  Kiup.iBk.co.kR
    • 126.117.125.213  oPEN.iBk.co.kR
    • 126.117.125.213  www.daum.NeT
    • 126.117.125.213  WOORiBaNk.coM
    • 126.117.125.213  haNmail.NeT
    • 126.117.125.213  eBaNk.keB.co.kR
    • 126.117.125.213  www.gmARket.co.kr
    • 126.117.125.213  oNliNe.keB.co.kR
    • 126.117.125.213  oPEN.keB.co.kR
    • 126.117.125.213  www.haNmail.Net
    • 126.117.125.213  oPEN.hanABaNk.com
    • 126.117.125.213  www.hanAcBs.coM
    • 126.117.125.213  kfCc.co.kR
    • 126.117.125.213  www.kfcc.co.kR
    • 126.117.125.213  iBs.kfcc.co.kR
    • 126.117.125.213  EPostBaNk.go.kR
    • 126.117.125.213  www.EPostBaNk.go.kR
    • 126.117.125.213  www.nAte.com
"

Step 7

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


Did this description help? Tell us how we did.