You can use Marketo to update the value of a field by utilizing the Change Data Value flow action.
You can also block a field from being updated. See Block Updates to a Field for details.
In your Smart Campaign’s Flow tab, bring over the Change Program Member Data flow step and choose the desired program.
Find and select the attribute you want to change the value of.
Enter the Attribute value you want.
You can also use tokens in New Value.
Now just run the Smart Campaign, and you’re done!
If you want to clear the fields instead of updating them, you can enter “NULL” (no quotes, all caps) as the New Value.