Zilliacus began his IT career in 1978 as a Systems Programmer at Nokia Oy, writing parts of the operating system software for a major Finnish banking initiative. In 1980 he worked as a Systems Programmer for the Finnish army in a defence project. The following two years he wrote software for the Finnish paper industry.
In 1982 he joined Xerox Finland as a Systems Analyst. From 1984 to 1987 Stefan held the position of marketing manager for Xerox’s European HQ in London. He returned to Xerox Finland in 1988 as support manager, moving then to marketing manager and finally to sales director. In 1994 he was promoted to business manager for the Nordic countries and in 1997 his reporting line moved from the UK to the US.
Zilliacus has a degree in Electrical engineering from the Helsinki University of Technology and an MBA in economics and marketing from the Helsinki University of Economics.