Over 40,000 firms, including energy providers, banks and hospitals could be required to report cyber-break-ins under new rules proposed by the EU.
It is part of a move to intensify global efforts to fight cybercrime.
Digital agenda commissioner Neelie Kroes said that Europe needed to improve how it dealt with cybersecurity.
But firms are concerned that reporting online attacks and security breaches might damage their reputations.
Read more on BBC.
The European Commission has issued a Proposed Directive on Network and Information Security – frequently asked questions. From the FAQ, examples of companies that would be required to report significant breaches:
Read the full memo here.