Securing VMWare Guest OSs
Maintain VMWare Guest OSs as you maintain other security-critical resources in your organization. For example:

Keep up to date on security patches for OS and third-party applications.

Use the OS firewall in addition to other security mechanisms.

Take appropriate backups.

Protect data stored in the virtualized environment.

Follow best practices for applications, including:

Change all default passwords.

Use encryption on network connections as appropriate.

Enable and review security audit.