The Welchia worm (also known as Nachi) is a Nematode or friendly worm that deletes Blaster and patches the vulnerabilities that made Blaster possible. While Welchia often came to the aid of users suffering from the Blaster Worm, it tended to slow computers down while it carried out its non-malevolent intentions, and was a bit of a nuisance for those who had already got Blaster removed from their PCs.