Do you want to send encrypted files, or do you want better security against outsiders getting access to your wireless network?
File sharing can be dangerous if you leave the default "everyone" in the users list for shared folders.
You need to assign only those users you want to have access to your shares any permissions. Don't give anyone full privs, unless you completely trust the user, and don't give modify unless you want to allow someone to change your files.
You can remove or add users from the share permissions, and only those who are listed will have any access to your shares.
In the folder options, uncheck "use simple file sharing". This will allow you to set a more specific security policy.
Use the Sharing tab to set permissions for users who will access the folders across the network.
Use the Security tab to set permissions for local users (those who log onto the machine locally).
FW