Illegal Entry Protocols
By 2521, UNSC military operating systems had been standardized for over the last seventy years, leaving them vulnerable to Insurrectionist hacking. This stood in contrast to the Outer Colony networks used by the insurgents: as makeshift software, they were much more heterogeneous in nature and thus more difficult for the UNSC to decipher. There were several incidents in which UNSC systems had been hacked by rebel forces, the most prominent being the destroyer UNSC Persephone. This prompted Dr. Halsey to create new security protocols for the UNSC.
Based on already existing translation algorithms, the Illegal Entry Protocols were created by Dr. Halsey primarily for use in third-generation smart AIs. This new crop of intellect would allow them to penetrate any system software. A side effect of the protocol was that the AIs could learn to mutate and defend established UNSC operations systems from attacks. Later, the protocols were used by AIs to reverse-engineer Covenant technology, namely the energy shielding of the Kig-Yar point defense gauntlet.
To Dr. Halsey's chagrin, the Illegal Entry Protocols and Counter-Illegal Entry Protocols soon gained the nicknames "PIE" and "C-PIE", respectively, derived from misspellings of their acronyms.