Use the following python script/s to pull a website's favourite icon and hash it using MurmurHash3.
Shodan uses mmh3 to hash favicons and these are indexed during their periodic crawls.
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# python 2
import mmh3
import requests
response = requests.get('https://domain.com/favicon.ico')
favicon = response.content.encode('base64')
hash = mmh3.hash(favicon)
print hash
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# python 3
import mmh3
import requests
import codecs
response = requests.get('https://domain.com/favicon.ico')
favicon = codecs.encode(response.content,"base64")
hash = mmh3.hash(favicon)
print(hash)