All network connections are protected by a 128bit stream cipher using a session key created from a 512bit Diffie-Hellman key exchange. So, network logs cannot be used to identify what network passed through the system. You can easily set up your own separate Blocks network or join a public one. You can even participate in a public Blocks network when you are behind a firewall that stops incoming connections. Blocks uses very little resources so you can use your computer for other things while you are running your Blocks server.
Blocks is completely public domain.
When you run a Blocks server it finds and connects to a number of other Blocks servers, creating an interconnected 'network' of servers. All Blocks servers have a disk bound cache of data that is used to store data in the form of fixed size binary blocks of 64Kb. When you 'upload' a file to your blocks server, the file is split into 64Kb blocks and each is inserted into the cache. A 'header' block containing a list of identifiers for all the data blocks, as well as basic information such as the filename and size, is also inserted into the cache, and the file is advertised to the blocks network. The server also uses the cache to store data as it is routed and downloaded so eventually your uploaded file data will be overwritten.