Increase organic search affinity score for users coming to site from a search engine?

[Anonymous]

We have affinity scores for the different channels and am wondering how to set this up for organic search. For example with paid search, when a user visits our site from paid search there is a gclid parameter in the URL for goole that we can use to increase a paid search channel affinity score. How can we change the affinity score for visitors from organic search? Is there a trigger that identifies the referring URL as google/yahoo/bing other than original referrer (which will only work once)?

[Josh_Hill13]

You can add a new field Most Recent Referrer to pull in organic data. I believe it is possible to setup code on the site that improves the ability to see this data and drop it into Marketo.