Implement security for sharepoint lists

Question

I have a share-point list with which I want to implement three things:

1. Freeze some columns so that their data can be edited by specific people only like the ones within site owners group with full privileges.

2. Hide some columns according to some user groups. Earlier I did this by creating two views, one with limited columns selected and visible to all and one with all columns with filter Restricted_user = [Me] and I have put all users' names from active directory in that field, but I guess it has security loopholes like someone could see all row data by selecting view item and everything in that row will be visible to him.

   2.1. If my own second option approach is selected can I implement this comparison with group aliases, rather than individuals so that I have to put only group aliases in that column field, rather that all names in that group aliases.

3. Last but not the least can i break up list rows into two categories so that two different groups can access and edit their own data only.Eg. 20 rows are there 5 accessible to group1 and 15 accessible to group2 but they cant access each others data rows.

Apologies for long question.

Answer 1

The most secure way to accomplish #3 is using item level permissions. Less secure ways include custom views and audiences.

For #1 and #2, you will need to create custom field types. Out of the box SharePoint list columns do not support column based security.