Author: Francis Xavier Antazo   
 Modified By:: Rhena Inocencio

 

Worm:Win32/Conficker.B (Microsoft), W32/Conficker.worm (McAfee), Mal/Conficker-C (Sophos)

 PLATFORM:

Windows

 OVER ALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE
Low
Medium
High
Critical

  • Threat Type:
    Worm

  • Destructiveness:
    No

  • Encrypted:
    Yes

  • In the wild:
    Yes

  OVERVIEW

INFECTION CHANNEL: Propagates via flashdrives, Copies itself in all available logical drives, Propagates via network shares

This worm arrives via removable drives. It may be dropped by other malware.

It modifies registry entries to disable various system services. This action prevents most of the system functions to be used. It deletes registry entries, causing some applications and programs to not function properly.

It drops copies of itself into all the removable drives connected to an affected system. It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system. It exploits software vulnerabilities to propagate to other computers across a network.

It uses certain lists of user names and passwords to access password-protected shared files.

It prevents users from visiting antivirus-related websites that contain specific strings.

  TECHNICAL DETAILS

File size: 166,111 bytes
File type: DLL
Memory resident: Yes
INITIAL SAMPLES RECEIVED DATE: 05 апреля 2016
PAYLOAD: Compromises system security, Compromises network security

Arrival Details

This worm arrives via removable drives.

It may arrive via network shares.

It may be dropped by other malware.

Installation

This worm drops the following copies of itself into the affected system:

  • %Application Data%\{random file name}.dll
  • %System%\{random file name}.dll
  • %System%\{random number}.tmp
  • %Program Files%\Internet Explorer\{random file name}.dll
  • %Program Files%\Movie Maker\{random file name}.dll
  • %User Temp%\{random file name}.dll

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.. %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.. %Program Files% is the Program Files folder, where it usually is C:\Program Files on all Windows operating system versions; C:\Program Files (x86) for 32-bit applications running on Windows 64-bit operating systems.. %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

Autostart Technique

This worm 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\{random characters}
DisplayName = "{random}"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random characters}
Type = "32"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random characters}
Start = "2"

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

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random characters}
ObjectName = "Local System"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random characters}
Description = "{long sentences}"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random characters}
ImagePath = "%System Root%\system32\svchost.exe -k netsvcs"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random characters}\Parameters
ServiceDll = "%System%\{malware file name}"

It adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random characters} = "rundll32.exe {malware path and file name}, {Parameter}"

Other System Modifications

This worm adds the following registry entries as part of its installation routine:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Applets
dl = "0"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Applets
ds = "0"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Applets
ds = "0"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Applets
dl = "0"

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Tcpip\Parameters
TcpNumConnections = "0x00FFFFFE" - hex values

(Note: The default value data of the said registry entry is {System Default}.)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\SvcHost
netsvcs = "{original value} {random characters}"

(Note: The default value data of the said registry entry is {original value}.)

It modifies registry entries to disable the following system services:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wuauserv
Start = "4"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\WinDefend
Start = "4"

(Note: The default value data of the said registry entry is 2.)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\ERSvc
Start = "4"

(Note: The default value data of the said registry entry is 2.)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\WerSvc
Start = "4"

(Note: The default value data of the said registry entry is 2.)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wscsvc
Start = "4"

(Note: The default value data of the said registry entry is 2.)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\BITS
Start = "4"

(Note: The default value data of the said registry entry is 2.)

It modifies the following registry entries to hide files with Hidden attributes:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\explorer\
Advanced\Folder\Hidden\
SHOWALL
CheckedValue = "0"

(Note: The default value data of the said registry entry is 1.)

It deletes the following registry keys:

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\explorer\
ShellServiceObjects\{FD6905CE-952F-41F1-9A6F-135D9C6622CC}

It deletes the following registry entries:

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Run
Windows Defender = "{value}"

Propagation

This worm creates the following folders in all removable drives:

  • {drive letter}:\RECYCLER\{SID}

It drops copies of itself into all the removable drives connected to an affected system.

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

  • {drive letter}:\RECYCLER\{SID}\{random characters}

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

The said .INF file contains the following strings:

;garbage characters
;garbage characters
shelLExECUte =RuNdLl32.EXE .\RECYCLER\S-5-3-42-2819952290-8240758988-879315005-3665\jwgkvsq.vmx,ahaezedrn
;garbage characters
;garbage characters

It exploits the following software vulnerabilities to propagate to other computers across a network:

Information Theft

This worm uses the following lists of user names and passwords to access password-protected shared files:

  • 99999999
  • 9999999
  • 999999
  • 99999
  • 88888888
  • 8888888
  • 888888
  • 88888
  • 77777777
  • 7777777
  • 777777
  • 77777
  • 66666666
  • 6666666
  • 666666
  • 66666
  • 55555555
  • 5555555
  • 555555
  • 55555
  • 44444444
  • 4444444
  • 444444
  • 44444
  • 33333333
  • 3333333
  • 333333
  • 33333
  • 22222222
  • 2222222
  • 222222
  • 22222
  • 11111111
  • 1111111
  • 111111
  • 11111
  • 00000000
  • 0000000
  • 00000
  • 0987654321
  • 987654321
  • 87654321
  • 7654321
  • 654321
  • 54321
  • zzzzz
  • xxxxx
  • qqqqq
  • aaaaa
  • intranet
  • controller
  • killer
  • games
  • private
  • market
  • coffee
  • cookie
  • forever
  • freedom
  • student
  • account
  • academia
  • files
  • windows
  • monitor
  • unknown
  • anything
  • letitbe
  • letmein
  • domain
  • access
  • money
  • campus
  • explorer
  • exchange
  • customer
  • cluster
  • nobody
  • codeword
  • codename
  • changeme
  • desktop
  • security
  • secure
  • public
  • system
  • shadow
  • office
  • supervisor
  • superuser
  • share
  • super
  • secret
  • server
  • computer
  • owner
  • backup
  • database
  • lotus
  • oracle
  • business
  • manager
  • temporary
  • ihavenopass
  • nothing
  • nopassword
  • nopass
  • Internet
  • internet
  • example
  • sample
  • love123
  • boss123
  • work123
  • home123
  • mypc123
  • temp123
  • test123
  • qwe123
  • abc123
  • pw123
  • root123
  • pass123
  • pass12
  • pass1
  • admin123
  • admin12
  • admin1
  • password123
  • password12
  • password1
  • default
  • foobar
  • foofoo
  • temptemp
  • testtest
  • rootroot
  • adminadmin
  • mypassword
  • mypass
  • Login
  • login
  • Password
  • password
  • passwd
  • zxcvbn
  • zxcvb
  • zxccxz
  • zxcxz
  • qazwsxedc
  • qazwsx
  • q1w2e3
  • qweasdzxc
  • asdfgh
  • asdzxc
  • asddsa
  • asdsa
  • qweasd
  • qwerty
  • qweewq
  • qwewq
  • nimda
  • administrator
  • Admin
  • admin
  • a1b2c3
  • 1q2w3e
  • 1234qwer
  • 1234abcd
  • 123asd
  • 123qwe
  • 123abc
  • 123321
  • 12321
  • 123123
  • 1234567890
  • 123456789
  • 12345678
  • 1234567
  • 123456
  • 12345

Other Details

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

  • http://www.{BLOCKED}p.org
  • http://www.{BLOCKED}yipaddress.com
  • http://www.whatismyip.org
  • http://checkip.dyndns.org

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

  • myspace.com
  • msn.com
  • ebay.com
  • cnn.com
  • aol.com
  • w3.org
  • ask.com
  • yahoo.com
  • google.com
  • baidu.com

It does the following:

  • Patches TCPIP.SYS in memory in order to modify the limit of maximum TCP half-connection attempts in systems running Windows XP Service Pack 2. It does this by loading TCPIP.SYS in a certain memory location. It then drops %System%\0{random number}.tmp, which is responsible for creating a device object named TcpIp_Perf and linking it to the loaded TCPIP.SYS in memory. It then sends the control code (patch code) to the linked device object.
  • Exports functions used by other malware. It sets the creation time of the file similar to that of the creation time indicated in the legitimate Windows file KERNEL32.DLL, which is also located in the Windows system folder. It does this to prevent early detection as a newly added file on the affected system.
  • Executes the following commands to disable auto-tuning if the system is running under Windows Vista:
    • netsh interface tcp set global autotuning=disabled
  • Propagates by taking advantage of a vulnerability discovered in certain Microsoft operating systems that could allow remote code execution if an affected system received a specially crafted RPC request, which also contains a shellcode. More information on the said vulnerability can be found in this Microsoft Web page:
    • Microsoft Security Bulletin MS08-067
    Once this specially crafted RPC request reaches its target vulnerable system, the shellcode is decrypted, and then retrieves certain APIs capable of downloading a copy of the worm from the affected system, which is already converted into an HTTP server. The affected system then opens a random TCP port, allowing the vulnerable machine to connect to itself using the following URL:
    • http://{IP address of the affected machine}:{random port generated by this worm}/{malware file name composed of random characters}
  • Propagating over the Internet by attempting to send the exploit code to random Internet addresses. It first broadcasts the opened random port that serves as an HTTP server so that it is accessible over the Internet. Then, it gets the external IP address of the system to check if it has a direct connection to the Internet. Once a direct connection is made, it launches the exploit code over the Internet by checking the external IP address and the configured IP address in the ethernet or modem driver.
  • Drops a copy of itself in the Admin$\System32 folder using a randomly named file using the credentials of the compromised user once it gains access. Upon successful network propagation, a scheduled task is created in the %Windows%\Tasks folder using the NetScheduleJobAdd API to be able to execute its dropped copy. The scheduled time of execution on the created job file is retrieved from GetLocalTime API.
  • Generates strings and appends the following extensions to create URLs based on the current date:
    • .biz
    • .info
    • .org
    • .net
    • .com.
    • .ws
    • .cn
    • .cc
  • Generates a set of URLs containing 250 random sites per day based on the UTC time standard.
  • Checks if any of the generated URLs is active and creates a thread to download and execute files. This routine also converts the host name to an IP address to complete the following URL:
    • http://{IP address}/search?q=0
    The NetpwPathCanonicalize_hook in NETAPI32.DLL has a function which checks for a generated URL in the RPC traffic. If the URL is active, it will attempt to download the hosted file.
  • Creates a named pipe with the following format:
    • \.\pipe\System_{random number}
    It then connects to the pipe to read data. The data obtained from the pipe is be passed to the call_create_thread_download function, which is responsible for downloading, validating, and executing the downloaded file.
  • Hooks the following APIs to filter a list of antivirus-related sites when being accessed on the Internet:
    • DnsQuery_A
    • DnsQuery_UTF8
    • Query_Main

It prevents users from visiting antivirus-related websites that contain the following strings:

  • ahnlab
  • arcabit
  • avast
  • avg
  • avira
  • avp
  • bit9.
  • castlecops
  • centralcommand
  • clamav
  • comodo
  • computerassociates
  • cpsecure
  • defender
  • drweb
  • emsisoft
  • esafe
  • eset
  • etrust
  • ewido
  • f-prot
  • f-secure
  • fortinet
  • gdata
  • grisoft
  • hacksoft
  • hauri
  • ikarus
  • jotti
  • k7computing
  • kaspersky
  • malware
  • mcafee
  • microsoft
  • networkassociates
  • nod32
  • norman
  • norton
  • panda
  • pctools
  • prevx
  • quickheal
  • rising
  • rootkit
  • sans.
  • securecomputing
  • sophos
  • spamhaus
  • spyware
  • sunbelt
  • symantec
  • threatexpert
  • trendmicro
  • virus
  • wilderssecurity
  • windowsupdate
  • Ccert.

  SOLUTION

Minimum scan engine: 9.800
First VSAPI Pattern File: 12.448.07
First VSAPI Pattern Release Date: 05 апреля 2016
VSAPI OPR PATTERN-VERSION: 12.449.00
VSAPI OPR PATTERN DATE: 06 апреля 2016

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 WORM_DOWNAD.AC

Step 3

Restart in Safe Mode

[ learnMore ]

Step 4

Delete this registry key

[ learnMore ]

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 characters}

Step 5

Delete this registry value

[ learnMore ]

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
    • {random characters} = "rundll32.exe {malware path and file name}, {Parameter}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Applets
    • dl = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Applets
    • ds = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Applets
    • ds = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Applets
    • dl = "0"

Step 6

Restore these modified registry values

[ learnMore ]

Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SvcHost
    • From: netsvcs = "{original value} {random characters}"
      To: netsvcs = {original value}
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
    • From: TcpNumConnections = "0x00FFFFFE" - hex values
      To: TcpNumConnections = {System Default}
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\wuauserv
    • From: Start = "4"
      To: Start = 2
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WinDefend
    • From: Start = "4"
      To: Start = 2
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\ERSvc
    • From: Start = "4"
      To: Start = 2
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WerSvc
    • From: Start = "4"
      To: Start = 2
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\wscsvc
    • From: Start = "4"
      To: Start = 2
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\BITS
    • From: Start = "4"
      To: Start = 2
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\explorer\Advanced\Folder\Hidden\SHOWALL
    • From: CheckedValue = "0"
      To: CheckedValue = 1

Step 7

Search and delete AUTORUN.INF files created by WORM_DOWNAD.AC that contain these strings

[ learnMore ]
;garbage characters
;garbage characters
shelLExECUte =RuNdLl32.EXE .\RECYCLER\S-5-3-42-2819952290-8240758988-879315005-3665\jwgkvsq.vmx,ahaezedrn
;garbage characters
;garbage characters

Step 8

Search and delete this folder

[ learnMore ]
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 9

Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_DOWNAD.AC. 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 10

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.

  • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\explorer\ShellServiceObjects\{FD6905CE-952F-41F1-9A6F-135D9C6622CC}
  • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run (Value:Windows Defender )


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