DNAS
Sony Computer Entertainment Inc. uses DNAS (Dynamic Network Authentication System), a proprietary authentication system, to help protect copyright and security in connecting the PS2 or PSP™ system to a network. DNAS may retrieve information about a user's hardware and software for authentication, copy protection, account blocking, system, rules, or game management and other purposes. The information collected does not identify the user personally. The unauthorized transfer, exhibition, export, import or transmission of programs and devices circumventing its authentication scheme may be prohibited by law.
DNAS seems to be also used in the Broadband Navigator. See [1].
DNAS seems to use some data from the HDD. See Hard_Drive#Security_and_authentication.
See also
https://manuals.playstation.net/document/en/psp/current/settings/dnas.html
https://www.psx-place.com/threads/wip-new-ps2-dnas-dns-host-for-remaining-online-games.22142/
https://github.com/FogNo23/DNASrep
DNAS replacement server
https://github.com/Horizon-Private-Server/horizon-server
horizon-server is only used for medius, not DNAS
https://github.com/VTSTech/VTSTech-SRVEmu
VTSTech-SRVEmu was an ambitious project to be a multi-game server emulator for games utilizing a protocol used in many EA games