Campus is now advising everyone to change our Kerberos passphrases. Go to computingaccounts.ucdavis.edu, select "Change your passphrase," and follow the instructions.
You should not use your Kerberos passphrase for any non-UC services. Re-using passwords increases the risk of a breach.
Seriously consider changing your passphrases for other services, such as banks and retailers, once they have fixed their own vulnerabilities.
Do not respond to suspicious email messages, especially when they ask you for your passphrase or other personal information. More information is available at security.ucdavis.edu.