Rishi Sunak said he was limited in what he could say over who was to blame for a "malign act" on the Ministry of Defence website.
He said China has "fundamentally different values to ours" but would not name it is as the suspect over a cyber attack.
But he named Russia, Iran, North Korea and China as a “mix of authoritarian states” and said it was right to increase defence spending.
Defence Secretary Grant Shapps will give a statement in the House of Commons later.
MoD data breach: China suspected of hacking UK armed forces payroll