Analysis by: Sabrina Lei Sioting

ALIASES:

Trojan:Win32/Alureon.CO [Microsoft]; Trojan.Win32.TDSS.chhz [Kaspersky]; Trojan.Gen [Symantec]; DNSChanger.cc [McAfee]; Mal/TDSSPack-AF [Sophos]; Trojan.Win32.FakeSmoke.c [Sunbelt]; Trojan.Win32.Tdss [Ikarus]; Win32/Olmarik.YR trojan [Nod32];

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Dropped by other malware, Downloaded from the Internet

TROJ_ZLOB.FZO can retrieve stored user names and passwords. If successful, the information is send to a specific site, making the network vulnerable to remote attacks.

This Trojan changes the DNS settings of the affected system. As a result, connections from the affected system passes through the attacker's system and enables the attacker to control and monitor communications.

It also monitors Internet browsers to observe search engines. Search results are intercepted by the malware. After a timeout of 10 seconds, the malware changes the search results and redirects users to a random page.

This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

  TECHNICAL DETAILS

File Size: 72,192 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 13 Jan 2010
Payload: Compromises system security, Connects to URLs/IPs, Steals information, Terminates processes, Compromises network security

Arrival Details

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

  • %Application Data%\{random}.exe

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Windows\Profiles\{user name}\Application Data on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Application Data on Windows NT, and C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003.)

It uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • Global\{random}

It injects codes into the following process(es):

  • spoolsv.exe
  • explorer.exe

Autostart Technique

The scheduled task executes the malware every:

  • At User Login

Other System Modifications

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Security Center
UacDisableNotify = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
system
EnableLUA = "0"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\DomainProfile\AuthorizedApplications\
List
%System%\spoolsv.exe = "%System%\spoolsv.exe:*:Enabled:spoolsv.exe"

It modifies the following registry key(s)/entry(ies) as part of its installation routine:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Tcpip\Parameters
NameServer = "{BLOCKED}.162.160,{BLOCKED}.166.191 "

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

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Tcpip\Parameters
DhcpNameServer = "{BLOCKED}.162.160,{BLOCKED}.166.191 "

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

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Tcpip\Parameters\
Interfaces\{CLSID}
DhcpNameServer = "{BLOCKED}.162.160,{BLOCKED}.166.191 "

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

Dropping Routine

This Trojan drops the following files:

  • %System%\ernel32.dll - detected as TROJ_TDSS.SMET
  • %System%\spool\prtprocs\w32x86\{random}.dll - detected as TROJ_TDSS.SMET

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

Download Routine

This Trojan downloads an updated copy of itself from the following website(s):

  • http://{BLOCKED}lume.com/kx.php

NOTES:

It terminates the processes related to the following:

  • WinDefend
  • DisableAntiSpyware
  • Windows Defender

It uses Simple Object Access Protocol (SOAP) to find the network routers and get the following information:

  • manufacturer
  • modelName
  • modelNumber
  • controlURL

It accesses the control URL of the router depending on the discovered UPnP device:

  • http://{control URL}/index.asp
  • http://{control URL}/dlink/hwiz.html
  • http://{control URL}/home.asp
  • http://{control URL}/wizard.htm
  • http://{control URL}/login.asp

It uses brute force to access the routers using the following strings:

[Username]

  • admin
  • {blank}
  • root
  • Admin
  • 1234

[Password]
  • Password
  • pass
  • password
  • root
  • router
  • admin
  • administrator
  • {blank}
  • 0
  • 0P3N
  • 1234
  • 12345
  • 123456
  • a
  • a6a7wimax
  • adslnadam
  • adslroot
  • airlive
  • alice
  • atlantis
  • bewan
  • cableroot
  • cciadmin
  • conexant
  • ecom
  • epicrouter
  • friend
  • hamlet
  • hayesadsl
  • highspeed
  • hsparouter
  • motorola
  • mysweex
  • password1
  • sitecom46
  • sky
  • smcadmin
  • stccpe_2007
  • telekom
  • telus
  • telus177
  • tmadmin
  • trendchip
  • ttnet
  • utstar
  • vodafone
  • zoomadsl

It can also retrieve stored user names and passwords in by using the CredEnumerateA function and GID abe2869f-9b47-4cd9-a358-c22904dba7f7. If successful, the malware adds an open port and retrieve the external IP address of the router. The information is send to the following site, making the network is vulnerable to remote attacks:

  • http://{BLOCKED}0.26/bsfd.php

In addition to opening a port in the router, it also changes the DNS settings of the affected system to the following:

  • Preferred DNS Server: {BLOCKED}.243.170
  • Alternate DNS Server: {BLOCKED}.255.255
As a result, connections from the affected system passes through the attacker's system and enables the attacker to control and monitor communications.

It also monitors Internet browsers to observe search engines. Search results are intercepted by the malware. After a timeout of 10 seconds, the malware changes the search results and redirect users to a random page. It monitors the following browsers:

  • iexplore.exe
  • firefox.exe
  • safari.exe
  • opera.exe

It monitors the following search engines:

  • .google.
  • search.yahoo.
  • search.msn.
  • search.live.
  • altavista.com
  • ask.com
  • search.aol.
  • saerch.aol.
  • search.icq.
  • alltheweb.com
  • bing.com
  • yandex.ru
  • rambler.ru
  • go.mail.ru
  • sm.aport.ru

It monitors the following URL strings:

  • .youtube.
  • .wikipedia.
  • .yahoo.
  • rds.yahoo.
  • overture.
  • .yimg.com
  • wikimedia.
  • amazon.com
  • hotmail.
  • .msn.com
  • .live.com
  • microsoft.
  • altavista.
  • atdmt.com
  • wzus1.ask.
  • /i/i.gif?
  • opselect.com
  • aolcdn
  • aolsearch
  • .aol.
  • revsci.net
  • atwola.
  • digitalcity.
  • .icq.
  • o.aolcdn.com
  • alltheweb.
  • bing.
  • .yandex.
  • tns-counter.
  • .rambler.
  • .rl0.ru
  • .begun.
  • list.ru
  • .mail.ru
  • z5x.net
  • imgsmail.ru
  • .aport.
  • yadro.ru
  • .ag.ru

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 6.766.05
FIRST VSAPI PATTERN DATE: 13 Jan 2010
VSAPI OPR PATTERN File: 6.767.00
VSAPI OPR PATTERN Date: 14 Jan 2010

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 TROJ_ZLOB.FZO

     TROJ_TDSS.SMET

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_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\DomainProfile\AuthorizedApplications\List
    • %System%\spoolsv.exe = "%System%\spoolsv.exe:*:Enabled:spoolsv.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Security Center
    • UacDisableNotify = 1
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\system
    • EnableLUA = 0

Step 5

Restore this modified 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\Tcpip\Parameters
    • From: NameServer = {BLOCKED}.162.160,{BLOCKED}.166.191
      To: {user defined}
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
    • From: DhcpNameServer = {BLOCKED}.162.160,{BLOCKED}.166.191
      To: {user defined}
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\{CLSID}
    • From: DhcpNameServer = {BLOCKED}.162.160,{BLOCKED}.166.191
      To: {user defined}

Step 6

To delete the added job file:

  1. Click on Start>Programs>Accessories>System Tools>Scheduled Tasks
  2. Double-click on a job file.
  3. Check if the malware path and file name is in the Run: box.
  4. If it does, delete the job file.
  5. Repeat step 2-4 for the remaining job files.

Step 7

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