Unknown attackers used a spearphishing campaign to compromise sensitive systems operated by the Internet Corporation for Assigned Names and Numbers (ICANN), a coup that allowed them to take control of employee e-mail accounts and access personal information of people doing business with the group. ICANN, which oversees the Internet's address system, said in a release published Tuesday that the breach also gave attackers administrative access to all files stored in its centralized zone data system, as well as the names, postal addresses, e-mail addresses, fax and phone numbers, user names, and cryptographically hashed passwords of account holders who used the system.