On macOS, two backup programs are doing this: * https://www.shirt-pocket.com/SuperDuper/SuperDuperDescription.html https://www.shirt-pocket.com/SuperDuper/Supe

On macOS, two backup programs are doing this: * https://www.shirt-pocket.com/SuperDuper/SuperDuperDescription.html https://www.shirt-pocket.com/SuperDuper/SuperDuperDescriptio... * https://bombich.com https://bombich.com Also, Little Snitch, a network monitoring/firewall tool: * https://www.obdev.at/products/littlesnitch/index.html https://www.obdev.at/products/littlesnitch/index.html