Well I am not very sure about Digital Sourcing, but ya Active Sourcing & Passive Sourcing I can help you out.
Active sourcing is nothing but finding candidates from job portal. Those are active candidates who are looking out for job actively in market, and as these people are actively looking for job, they do have their resume available on job portal.
While Passive couring is nothing but finding candidates apart from job portal. These are the best candidates and they do have some where or other their presence on internet/www.
There are N number of social networking websites which do provide profiles of these candidates and some websites which do provide contact information.
Google is the best way to find passive candidate. An google query for your example is given below.
(intitle:resume OR intitle:cv OR intitle:viate OR intitle:profile OR intitle:bio OR inurl:resume OR inurl:cv OR inurl:viate OR inurl:profile OR inurl:bio) AND (keyword OR "phrase 1" OR "phrase 2" OR keyword) AND (location OR city OR zipcode OR country) AND (skill1 OR skill2 OR "skill with phrase") -job -jobs -sample
Social Networking Websites like, linkedin.com, jigsaw.com, zoominfo.com, twitter.com, facebook.com etc..
Contact information websites like, pipl.com, whitepages.com, etc...
iNext Executive Search, India.
Virtual Recruiter For US & UK market.