On the 15th of August, a backdoor Trojan, known as Troj/Graybird.A, was widely distributed in messages that claimed it was an update to fix the vulnerability used by Blaster. Of course, users who believed the message and executed the attachment did not fix the DCOM vulnerability, but opened a backdoor into their computer for attackers.
W32/Dumaru.A, which appeared on the 19th of August, sends itself in emails purporting to be from security@microsoft.com. It claims to be a patch for Internet Explorer, and warns, "There are dangerous virus in the Internet". If executed, it installs a backdoor that connects to an IRC server and awaits further commands.
It seems likely that the authors of the Graybird Trojan and the Dumaru virus saw the panic caused by Blaster's spread as the perfect opportunity to trick users into installing their backdoors. Users should always be suspicious of unsolicited attachments, even if they arrive from apparently trustworthy sources.