Conficker changed the way parts of the botnet communicated overnight, but little else of note has happened so far.
The malware is far from an April Fool's joke, but it's obviously a long way from the Skynet botnet, as depicted in Terminator 3, that some of the more fevered imaginings of the media hinted at. The main activity that accompanied the run-up to the activation date was the registration of dozens of new domain names designed to advertise rogue security packages in the guise of Conficker clean-up tools.
As widely predicted by security vendors beforehand, Conficker and its 1 April activation was more about hype rather than havoc. As F-Secure notes, worms with triggers have consistently failed to do anything on that date. Previous damp squibs include the Michelangelo virus (1992), CIH (1999), SoBig (2003), and MyDoom (2004).
Nonetheless, Conficker remains implanted on many computers, anywhere between 1-4 million, according to the latest estimates.
Conficker first began spreading in November, using a variety of techniques including the exploitation of a well-known Windows vulnerability. Once it secured a foothold on infected networks the worm is capable of spreading across network shares by exploiting weak password security. The malware is also capable of spreading using infected USB drives.