Modified by: Merianne Polintan
ALIASES:

Worm:Win32/Korgo.V (Microsoft), W32.Korgo.V (Norton), W32/Korgo-T (Sophos)

 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:

  • In the wild: Yes

  OVERVIEW

This worm 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: 78,985 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 16 Jul 2009

Arrival Details

This worm 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:

  • %System%\{random}.exe

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

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
Cryptographic Service = "%System%\{random}.exe"

Other System Modifications

This worm deletes the following files:

  • {malware path}\ftpupd.exe

It adds the following registry keys:

HKEY_LOCAL_MACHINE\Software\Microsoft\
Wireless

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\AppCompatFlags

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\AppCompatFlags\
Layers

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\AppCompatFlags\
Layers
%WINDOWS%\explorer.exe = "EnableNXShowUI"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Wireless
ID = "{random}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Wireless
Client = "1"

It deletes the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Disk Defragmenter =

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Windows Security Manager =

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
System Restore Service =

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Bot Loader =

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
SysTray =

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
WinUpdate =

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Windows Update Service =

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
avserve.exe =

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
avserve2.exeUpdate Service =

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
MS Config v13 =

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Windows Update =

Other Details

This worm connects to the following possibly malicious URL:

  • http://{BLOCKED}v.ru/index.php?id={random_string}&scn={number}&inf={number}&ver=19&cnt={random_string}
  • http://www.{BLOCKED}e.ru/index.php?id={random_string}&scn={number}&inf={number}&ver=19&cnt={random_string}
  • http://{BLOCKED}arch.ru/index.php?id={random_string}&scn={number}&inf={number}&ver=19&cnt={random_string}
  • http://{BLOCKED}hange.com/index.php?id={random_string}&scn={number}&inf={number}&ver=19&cnt={random_string}
  • http://{BLOCKED}d.biz/index.php?id={random_string}&scn={number}&inf={number}&ver=19&cnt={random_string}
  • http://{BLOCKED}a.ru/index.php?id={random_string}&scn={number}&inf={number}&ver=19&cnt={random_string}
  • http://{BLOCKED}-x.com/index.php?id={random_string}&scn={number}&inf={number}&ver=19&cnt={random_string}
  • http://{BLOCKED}bank.ru/index.php?id={random_string}&scn={number}&inf={number}&ver=19&cnt={random_string}
  • http://{BLOCKED}p.nu/index.php?id={random_string}&scn={number}&inf={number}&ver=19&cnt={random_string}
  • http://{BLOCKED}bank.ru/index.php?id={random_string}&scn={number}&inf={number}&ver=19&cnt={random_string}
  • http://{BLOCKED}bank.ru/index.php?id={random_string}&scn={number}&inf={number}&ver=19&cnt={random_string}
  • http://{BLOCKED}empire.com/index.php?id={random_string}&scn={number}&inf={number}&ver=19&cnt={random_string}
  • http://{BLOCKED}kat.org/index.php?id={random_string}&scn={number}&inf={number}&ver=19&cnt={random_string}
  • http://{BLOCKED}ank.ru/index.php?id={random_string}&scn={number}&inf={number}&ver=19&cnt={random_string}
  • http://{BLOCKED}e.{BLOCKED}b.net/index.php?id={random_string}&scn={number}&inf={number}&ver=19&cnt={random_string}
  • http://{BLOCKED}ka.ru/index.php?id={random_string}&scn={number}&inf={number}&ver=19&cnt={random_string}
  • http://{BLOCKED}.{BLOCKED}.0.1:800/e.exe

  SOLUTION

Minimum Scan Engine: 9.300

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

Restart in Safe Mode

[ Learn More ]

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.

 
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Cryptographic Service = "%System%\{random}.exe"

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\SOFTWARE\Microsoft
    • Wireless
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion
    • AppCompatFlags
In 

Step 5

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

Step 6

Restore these deleted registry keys/values from backup

*Note: Only Microsoft-related keys/values will be restored. If the malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Disk Defragmenter
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Windows Security Manager
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • System Restore Service
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Bot Loader
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • SysTray
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • WinUpdate
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Windows Update Service
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • avserve.exe
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • avserve2.exeUpdate Service
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • MS Config v13
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Windows Update

NOTES:

Restore the deleted file {Malware Path}\ftpupd.exe from backup.


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