To those unversed or inexperienced in the ways of hacking, the HackNet is a technological nirvana in which the physical plane gives way to an environment composed of data in its purest form.
For those in the know, HackNet is the only method by which the most powerful of cybersecurity systems can be circumvented. By using an appropriately upgraded hacktool, experienced hackers have devised a way to temporarily convert their consciousness into a stream of binary data, which is then uploaded into the system.
With an avatar serving as their body inside HackNet, hackers can essentially traverse a world within a world, journeying from place to place by infiltrating any systems which are electronically linked together. With how ingrained into daily life the technology of Neocron has become, this means that a person entering the HackNet through a CityCom terminal in the Military Base could theoretically infiltrate a corporate terminal in Neocron itself, many miles to the south.
Of course, hackers would readily say that getting into the HackNet is a trial in itself and, once there, the enormity of what's possible with (what started out as) a store-bought hacktool can finally be realised.