That sounds eerily similar to the plot to the Channel 4 TV movie Killer Net
, except that there's no real horror character involved and it involves simply murdering (no dismembering) people online. So maybe I'm wrong anyhow about the similarites?
The movie was given such a critical, almost-nationwide slating though, that there's a great page which highlights the bad and cringeworthy stuff and makes mockeries of the flick and produces several shout-at-the-screen moments, MST3K-stylee.
to see this joyful experience.