Not so much split personality, but man-in-the-middle

Via Bruce Schneier:

The trouble began last year when he noticed strange things happening: files went missing from his computer; his Facebook picture was changed; and texts from his daughter didn’t reach him or arrived changed. “Nobody believed me,” says Gary. “My wife and my brother thought I had lost my mind. They scheduled an appointment with a psychiatrist for me.”

But he built up a body of evidence and called in a professional cybersecurity firm. It found that his email addresses had been compromised, his phone records hacked and altered, and an entire virtual internet interface created. “All my communications were going through a man-in-the-middle unauthorised server,” he explains.