Information about the W32.Blaster.worm

  • Thread starter Jerry Bryant [MSFT]
  • Start date


Jerry Bryant [MSFT]

PSS Security Response Team Alert - New Virus: W32.Blaster.worm

DATE: August 11, 2003
PRODUCTS AFFECTED: Windows XP, Windows 2000, Windows Server 2003, Windows NT
4.0, NT 4.0 Terminal Services Edition

The Microsoft Product Support Services Security Team is issuing this alert
to inform customers about a new worm named W32.Blaster.Worm which is
spreading in the wild. This virus is also known as: W32/Lovsan.worm
(McAfee), WORM_MSBLAST.A (Trendmicro), Win32.Posa.Worm (Computer
Associates). Best practices, such as applying security patch MS03-026 should
prevent infection from this worm.

Customers that have previously applied the security patch MS03-026 before
today are protected and no further action is required.

IMPACT OF ATTACK: Spread through open RPC ports. Customer's machine gets
re-booted or has mblast.exe exists on customer's system.

TECHNICAL DETAILS: This worm scans a random IP range to look for vulnerable
systems on TCP port 135. The worm attempts to exploit the DCOM RPC
vulnerability patched by MS03-026.

Once the Exploit code is sent to a system, it downloads and executes the
file MSBLAST.EXE from a remote system via TFTP. Once run, the worm creates
the registry key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run "windows
auto update" = msblast.exe I just want to say LOVE YOU SAN!! bill

Symptoms of the virus: Some customer may not notice any symptoms at all. A
typical symptom is the system is rebooting every few minutes without user
input. Customers may also see:
- Presence of unusual TFTP* files
- Presence of the file msblast.exe in the WINDOWS SYSTEM32 directory

To detect this virus, search for msblast.exe in the WINDOWS SYSTEM32
directory or download the latest anti-virus software signature from your
anti-virus vendor and scan your machine.

For additional details on this worm from anti-virus software vendors
participating in the Microsoft Virus Information Alliance (VIA) please visit
the following links:

Network Associates:

Trend Micro:


Computer Associates:

For more information on Microsoft's Virus Information Alliance please visit
this link:

Please contact your Antivirus Vendor for additional details on this virus.

PREVENTION: Turn on Internet Connection Firewall (Windows XP or Windows
Server 2003) or use a third party firewall to block TCP ports 135, 139, 445
and 593; UDP ports 135, 139, 445 and 593; also UDP 69 (TFTP) for zombie bits
download and TCP 4444 for remote command shell. To enable the Internet
Connection Firewall in Windows:

1. In Control Panel, double-click Networking and Internet Connections, and
then click Network Connections.
2. Right-click the connection on which you would like to enable ICF, and
then click Properties.
3. On the Advanced tab, click the box to select the option to Protect my
computer or network.

This worm utilizes a previously-announced vulnerability as part of its
infection method. Because of this, customers must ensure that their
computers are patched for the vulnerability that is identified in Microsoft
Security Bulletin MS03-026. Install the
patch MS03-026 from Windows Update

As always, please make sure to use the latest Anti-Virus detection from your
Anti-Virus vendor to detect new viruses and their variants.

RECOVERY: Security best practices suggest that previously compromised
machine be wiped and rebuilt to eliminate any undiscovered exploits that can
lead to a future compromise. See Cert Advisory:
Steps for Recovering from a UNIX or NT System Compromise.

For additional information on recovering from this attack please contact
your preferred anti-virus vendor.


This article will be available within 24 hours.

As always please make sure to use the latest Anti-Virus detection from your
Anti-Virus vendor to detect new viruses and their variants.

If you have any questions regarding this alert please contact your Microsoft
representative or 1-866-727-2338 (1-866-PCSafety) within the US, outside of
the US please contact your local Microsoft Subsidiary. Support for virus
related issues can also be obtained from the Microsoft Virus Support
Newsgroup which can be located by clicking on the following link

PSS Security Response Team


Jerry Bryant - MCSE, MCDBA
Microsoft IT Communities

Get Secure!

This posting is provided "AS IS" with no warranties, and confers no rights.



Kenneth Gold

Have implemented all fixes on my home W2000. This is to
check whether my email facility is working finally. No
need to reply. Thanks for your email.

Aside: it took several attempts to download SP4 as well as
MS03-026 patch. Finally worked.

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