If your domain is popular and have some traffic, many people will try to hack your domain name, If anyhow they change the whois information of your domain name with change of registrar, you will not able to do any thing to get back your domain
To protect your domain Insure following steps.
1. You must have updated whois information
2. Your Email address at whois information at your domain should be working, and you should check your domain whois and your email at regular interval.
3. You must lock your domain name, this is a facility available at free at your domain control panel. This is the most crucial step to protect your domain from hack.
4. Renew your domain name much before your domain expiration date.
5. Don’t reveal your control panel username and password to any one. and don’t use the same information for all of your account.