jmLÂWith 10,000 secure (full) nodes, Zencash was 51% attacked with just $500,000 in mining hashrate last week. Just goes to show that its not the full nodes that secure the network, its the miners.
https://whatsonchain.com/tx/5d0a4641916ce027afd36a08adb99bbc6314ff4527b68465004df5b4b3ec5340