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W32/Netspree.worm

This page shows details and results of our analysis on the malware W32/Netspree.worm

Threat Detail

Malware Type: Virus

Malware Sub-type: Internet Worm

Discovery Date: 2003-01-27

Next Steps:

Overview

This is a virus detection. Viruses are programs that self-replicate recursively, meaning that infected systems spread the virus to other systems, which then propagate the virus further. While many viruses contain a destructive payload, it's quite common for viruses to do nothing more than spread from one system to another.


Minimum DAT

4245 (2003-01-29)

Updated DAT

4401 (2004-10-27)

 Minimum Engine

5.1.00

File Length

48,448 bytes

Description Added

2003-01-27

Description Modified

2003-01-29

Malware Proliferation

Characteristics

This is a network share propagating worm and IRC bot trojan. It attempts to spread by copying itself to the IPC$ share of remote workstations. This is a default admin share on WinNT/2K/XP systems, but does not typically exist on Win9x systems. The worm attempts to gain access to the share by trying weak administrator usernames and passwords. However, if the current credentials of the user who is logged in are sufficient, the worm will have the access required to propagate. Once the worm has access to the remote system, it uses the PSEXEC utility to copy and execute itself there.

The main executable, WIN32LOAD.EXE, is an IRC Bot trojan and downloader. When run, it copies itself to the WINDOWS SYSTEM (%SysDir%) directory and creates a registry run keys to load itself at startup:

  • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\
    Run "Windows Subsys" = "C:\WINDOWS\SYSTEM\WIN32LOAD.EXE" rundll32.dll,loadsubsys,loadsys,win32
  • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\
    RunServices "Windows Subsys" = "C:\WINDOWS\SYSTEM\WIN32LOAD.EXE" rundll32.dll,loadsubsys,loadsys,win32

Symptoms

Presence of the following files in the WINDOWS SYSTEM (%SysDir%) directory
  • PSEXEC.BAT
  • PSEXEC.EXE
  • LCP_NETBIOS.DLL
  • WIN32LOAD.EXE
Heavy Netbios traffic.

Method of Infection

When an active Internet connection is found, the trojan downloads a plugin file, lcp_netbios.dll. This plugin contains the PSEXEC utility and a batch file containing the instructions to connect to remote systems and PSEXEC commands, which are used to carry out the infection. The trojan also connect to a hardcoded IRC channel for the purpose of "broadcasting" the infected user's system information: CPU, IP, hostname, total memory, memory available, OS version, uptime, system variables, etc. It listens for instructions, such as download/execute locations and UDP and SYN flood attack targets An additional registry key is created:

  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa "restrictanonymous" = DWORD:0
This ensures that enumeration of shares is available during a null session.

Removal

All Users:
Use specified engine and DAT files for detection and removal.

Modifications made to the system Registry and/or INI files for the purposes of hooking system startup, will be successfully removed if cleaning with the recommended engine and DAT combination (or higher).

Additional Windows ME/XP removal considerations

Variants

United States - English