WORM_LECNA.A

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.

It modifies certain registry entries to hide file extensions.

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

It executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system. As of this writing, the said sites are inaccessible.

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:

• %System%\Recycler.exe

(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.)

It drops the following component file(s):

• %System%\uninstx.exe - also detected as WORM_LECNA.A
• %System%\confi.exe - also detected as WORM_LECNA.A
• %System%\{random file name}.dll - also detected as WORM_LECNA.A

(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.)

It drops the following non-malicious files:

• %System%\Config.ini
• %System%\AUTORUN.INF - used as the master copy of the AUTORUN.INF dropped in removable drives

(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.)

Its DLL component is injected to the following process(es):

• explorer.exe

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
Windows Recycled = "%System%\Recycler.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
uninstx.exe = "%System%\uninstx.exe"

Other System Modifications

This worm adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
NetWorkSetup

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
NetWorkSetup
pid = "{random string}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
NetWorkSetup
hostid = {random number}

It modifies the following registry entries to hide file extensions:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
HideFileExt = "1"

(Note: The default value data of the said registry entry is 0.)

Propagation

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

• {removable drive letter}:\Recycler.exe

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]
open=Recycler.exe
shellexecute=Recycler.exe
shell\Auto\command=Recycler.exe
shell=Auto

Process Termination

This worm terminates the following processes if found running in the affected system's memory:

• amon.exe
• armor2net.exe
• avgfwsrv.exe
• avp.exe
• blackd.exe
• blackice.exe
• bullguard.exe
• capfaem.exe
• ccapp.exe
• firesvc.exe
• fsaw.exe
• guard.exe
• kavpf.exe
• kavpfw.exe
• lpfw.exe
• mcagent.exe
• mpeng.exe
• npfsvice.exe
• ofcpfwsvc.exe
• outpost.exe
• pccguide.exe
• persfw.exe
• pf4.exe
• pnmsrv.exe
• rfwsrv.exe
• smc.exe
• sspfwtry2.exe
• swagent.exe
• tmpfw.exe
• winaw32.exe
• winroute.exe
• zlclient.exe

Download Routine

This worm accesses the following websites to download files:

• http://www.{BLOCKED}c.com/thrMilitary/thrapp.htm
• http://www.{BLOCKED}c.com/thrMilitary/thrmyapp.htm

It saves the files it downloads using the following names:

• %Windows%\netscv.exe
• %Windows%\netsvcs.exe

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

It then executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

As of this writing, the said sites are inaccessible.

NOTES:
It connects to following URLs to remotely inform a malicious user of its installation:

• http://{BLOCKED}h.com.cn/thrMilitary/thrconnect.gif
• http://www.{BLOCKED}c.com/thrMilitary/thrhostlist.htm

• devvect.dll
• funcdev.dll
• gatwaysh.dll
• getkbsyn.dll
• getspi.dll
• hostip2.dll
• kbpool.dll
• kbtype.dll
• keylsv.dll
• keyvect.dll
• lancheck.dll
• mcdirect8.dll
• mcfetch.dll
• missnetp.dll
• mousegrl.dll
• mpeg2fun.dll
• msrctr.dll
• netunnel.dll
• routersh.dll
• tcpproto.dll
• udpsh.dll
• vpntunnel.dll