Sophos Free Antivirus - Phishing/ Malware URL filtering

Hello,

I currently use Norton DNS + chrome + another antivirus to filter out malicious URLs.

I'm interested in how Sophos develops, collects and checks URLs to see if they are malicious or safe.

My questions are:

1) How does Sophos find links? Honey pots? Phishtank? Other public malware/phishing lists?

2) Will there be a large amount of overlap between the definitions Norton DNS and Sophos use for URL blocking?

3) At what stage are the URLs blocked by Sophos? Is it blocking connections to the IP after DNS resolution?

4) Are there any advanced techniques going on such as checking the contents of the page or checking the logo displayed on the page? In essence, generation something like a threat score similar to spam assassin for URLs?

5) Do any other companies provide malware links to you such as OpenDNS?

Many thanks,

Tom