Modified by: Christopher Daniel So
ALIASES:

VirTool:Win32/Injector.gen!B (Microsoft); Backdoor.Win32.IRCBot.lav (Kaspersky); Backdoor.Win32.IRCBot.lav (Sunbelt); W32/IRCBot.LAV!tr (Fortinet); W32/MalwareF.GODO (FProt); Win32/IRCBot.AMC (NOD32); Bck/IRCBot.CPM (Panda); SScope.Backdoor.Lanman (VBA32)

 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 via removable drives. It may be unknowingly downloaded by a user while visiting malicious websites.

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 takes advantage of software vulnerabilities to propagate across networks.

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

Ports: TCP port 445 (Microsoft-DS)
File Size: Varies
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 13 Aug 2009

Arrival Details

This worm arrives via removable drives.

It may be unknowingly downloaded by a user while visiting malicious websites.

Installation

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

  • %Windows%\system\dllcache.exe

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

It drops the following component file(s):

  • %System%\drivers\sysdrv32.sys - detected by Trend Micro as HKTL_TCPAGENT

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

It terminates the execution of the copy it initially executed and executes the copy it drops instead.

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
netmon = "%Windows%\system\dllcache.exe"

Other System Modifications

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

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\SafeBoot\Minimal\
dllcache
(Default) = "Service"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\SafeBoot\Network\
dllcache
(Default) = "Service"

It creates the following registry entry(ies) to bypass Windows Firewall:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%Windows%\system\dllcache.exe = "%Windows%\system\dllcache.exe:*:Microsoft Enabled"

Propagation

This worm 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.

The said .INF file contains the following strings:

[autorun]
shellexecute=strongkey-rc1.3-build-208.exe
action=Open folder to view files
shell\default=Open
shell\default\command=strongkey-rc1.3-build-208.exe
shell=default

It takes advantage of the following software vulnerabilities to propagate across networks:

Other Details

This worm deletes the initially executed copy of itself

NOTES:
It generates randomly generated IP address then attempts to establish a connection using TCP port 445. Once a successful connection is established, it then sends the exploited RPC request along with a copy of itself.

  SOLUTION

Minimum Scan Engine: 8.900
FIRST VSAPI PATTERN FILE: 6.366.04
FIRST VSAPI PATTERN DATE: 15 Aug 2009

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

Remove the malware/grayware file dropped/downloaded by WORM_IRCBOT.TFT

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

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.
%Windows%\system\dllcache.exe
%System%\drivers\sysdrv32.sys

Step 5

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
    • netmon="%Windows%\system\dllcache.exe"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SafeBoot\Minimal\dllcache
    • (Default)="Service"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SafeBoot\Network\dllcache
    • (Default)="Service"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • %Windows%\system\dllcache.exe="%Windows%\system\dllcache.exe:*:Microsoft Enabled"

Step 6

Search and delete AUTORUN.INF files created by WORM_IRCBOT.TFT that contain these strings

[ Learn More ]
[autorun]
shellexecute=strongkey-rc1.3-build-208.exe
action=Open folder to view files
shell\default=Open
shell\default\command=strongkey-rc1.3-build-208.exe
shell=default

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_IRCBOT.TFT. 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 8

Download and apply this security patch Refrain from using these products until the appropriate patches have been installed. Trend Micro advises users to download critical patches upon release by vendors.

NOTES:


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