Whois database contains information about administrator contact, billing contact and the technical contact for each domain name in the public WhoIs database. Anybody can access this information for any domain name. Spammers sometimes misuse this information for hacking purpose. Get more info about Whois.
Every domain owner has to provide accurate contact information. Now to question arise, how to protect this public information. You can protect public information with Whois Privacy service.
Some domain registrar like Namecheap offers complimantory whois privacy service while some other charges for this service.