Welchia

The Welchia worm, also known as the "Nachia worm," is a computer worm that exploits a vulnerability in the Microsoft Remote procedure call (RPC) service similar to the Blaster worm. However unlike Blaster, it tries to help the user by downloading and installing security patches from Microsoft, so it is a helpful worm. Though even as it implies no harm, it can increase network traffic, reboot the infected computer, and more importantly—it operates without consent and does not log anything. It has had several different variants and childworms. It was discovered on  August 18, 2003.
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