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The Blaster Worm (also known as Lovsan or Lovesan) was a computer worm that spread on computers running the Microsoft operating systems, Windows XP and Windows 2000, during August 2003.

The worm was first noticed and started spreading in the wild on August 11, 2003. The rate that it spread increased until the number of infections peaked on August 13, 2003. Filtering by ISPs and widespread publicity about the worm curbed the spread of Blaster.

On August 29, 2003, Jeffrey Lee Parson, an 18-year-old from Hopkins, Minnesota was arrested for creating the B variant of the Blaster worm; he admitted responsibility and was sentenced to an 18-month prison term in January 2005.

The worm was programmed to start a SYN flood on August 15, 2003 against port 80 of windowsupdate.com, thereby creating a distributed denial of service attack (DDoS) against the site. The damage to Microsoft was minimal as the site targeted was windowsupdate.com instead of windowsupdate.microsoft.com to which it was redirected. Microsoft temporarily shut down the targeted site to minimize potential effects from the worm.

The worm spread by exploiting a buffer overflow in the DCOM RPC service on the affected operating systems, for which a patch had been released one month earlier in MS03-026 and later in MS03-039.

The worm contains two messages hidden in strings. The first:

I just want to say LOVE YOU SAN!!

is why the worm is sometimes called the Lovesan worm. The second:

billy gates why do you make this possible ? Stop making money
and fix your software!!

is a message to Bill Gates, the co-founder of Microsoft, and the target of the worm.

Although the worm can only spread on systems running Windows 2000 or Windows XP (32 bit) it can cause instability in the RPC service on systems running Windows NT, Windows XP (64 bit), and Windows Server 2003. In particular, the worm does not spread in Windows Server 2003 because it was compiled with the /GS switch, which detected the buffer overflow and shut the RPCSS process down. [1] If the worm detects a connection to the Internet (regardless of dial-up or broadband), this can even lead to the system becoming so unstable that it displays the following message and then restarts (usually after 60 seconds):

Windows must now restart because the Remote Procedure Call
(RPC) Service terminated unexpectedly.

That was because either the /GS check code terminated or the buffer overflow crashed RPCSS. This was the first indication many users had of infection; it often occurred a few minutes after every startup on compromised machines. For reference, a user can move back the time or date on the system clock, gaining that amount of time before Windows restarts itself. For example, moving the date back one year will allow the user 365 days and 60 seconds before the system restarts itself, thus allowing time for disinfection. Another way to stop this message is to run shutdown -a.

• Timeline of notable computer viruses and worms
• List of convicted computer criminals
• Spam

• CERT Advisory CA-2003-20
• Security Response site from Symantec
• Article from Vnunet
• What You Should Know About Blaster
• Two Years Later, Blaster Worm Still Squirming
• More information for IT pros about Blaster Worm Virus from the Cisco Systems web site
• Linux-based approach to fixing MSBlaster Worm infection