Analysis by: Sabrina Lei Sioting
ALIASES:

Worm:Win32/Conficker.C (Microsoft), Win32/Conficker.AA worm (Symantec), W32/Conficker.worm.gen.a (Mcafee), Net-Worm.Win32.Kido.ih (Kaspersky)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

This worm arrives by connecting affected removable drives to a system. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It drops copies of itself into network drives. It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

  TECHNICAL DETAILS

File Size: 172,032 bytes
File Type: DLL
Memory Resident: No
Initial Samples Received Date: 29 Nov 2011

Arrival Details

This worm arrives by connecting affected removable drives to a system.

It 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 worm is a .DLL file that adds the following services:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random service name}
Type = "1"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random service name}
Start = "3"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random service name}
ErrorControl = "0"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random service name}
ImagePath = "%System%\{random number}.tmp"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random service name}
DisplayName = "{random service name}"

Propagation

This worm creates the following folders in all removable drives:

  • Recycler\{SID}

It drops the following copy(ies) of itself in all removable drives:

  • Recycler\{SID}\{random characters}.{random}

It drops copies of itself into network drives.

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

Other Details

This worm connects to the following URL(s) to get the affected system's IP address:

  • http://www.whatsmyipaddress.com
  • http://www.whatismyip.org
  • http://www.getmyip.org
  • http://checkip.dyndns.org

It connects to the following possibly malicious URL:

  • http://{DGA IP address}/search?q=0

It connects to the following time servers to determine the current date:

  • google.com

NOTES:

The dropped AUTORUN.INF file is detected as TROJ_DOWNAD.AD.

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 8.612.01
FIRST VSAPI PATTERN DATE: 29 Nov 2011
VSAPI OPR PATTERN File: 8.613.00
VSAPI OPR PATTERN Date: 30 Nov 2011

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 WORM_DOWNAD.AZ

  • TROJ_DOWNAD.AD

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\SYSTEM\CurrentControlSet\Services\{random service name}
    • Type = "1"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\{random service name}
    • Start = "3"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\{random service name}
    • ErrorControl = "0"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\{random service name}
    • ImagePath = "%System%\{random number}.tmp"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\{random service name}
    • DisplayName = "{random service name}"

Step 4

Search and delete these folders

[ 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.
  • {drive letter}:\Recycler\{SID}

Step 5

Scan your computer with your Trend Micro product to delete files detected as WORM_DOWNAD.AZ. 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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