Because of the relatively slow communications time between planets, both in normalspace and via HRNs, most data networks are planetary in scale. A datanet can send a query to another in-system world's datanet and receive an answer in no more than a couple of hours; data requests to other star systems travel via HRN and usually take at least a day.
Datanet use costs almost nothing. On most worlds it factors into an individual's comm and data service bill, usually about 10 credits a month total. Visitors can get temporary service for one credit per day, or sign up for a month at the standard rate. Inquiries to another planet's database usually cost about 1 credit for in-system requests, and up to 10 credits for a request from another system (the user does not incur additional communications fees unless he sends an actual transmission with his request for data).
With access to a planetary datanet, a character can tap into nearly the sum total of Human knowledge. Except on brand-new frontier colonies, the local datanet has a compressed version of the Imperial Library, with copies of nearly every book or video up to about a year before. Consulting older works costs nothing, but accessing new items may incur additional modest fees. As a general guideline, a datanet has KS: Everything This Society Knows 50- and SS: Every Science This Society Knows 30-, but the penalties listed in the sidebar on page 43 of Star Hero apply to rolls at the GM's discretion. The datanet can answer a simple question in just 1-3 Segments; more complex questions take longer (up to several hours, plus any relay time if the datanet must contact other datanets).
Because planetary datanets remain open to any Imperial citizen, for the most part there's no need to "jack" them (break into them to access or steal data). Some criminals jack the datanet simply so they don't have to pay for it at all. Others try to gain access to restricted or classified information — a difficult and time-consuming task Robust encryption protects even private civilian messages, and governmental/military encryption has so far proven unbreakable. The Empire stores most truly important or dangerous information on computer systems not hooked up to the datanet at all.
Anyone who uses the datanet leaves traces of his searches and activities. Government officials can find out the who, what, where, and when of any datanet use automatically; jackers can find out whether a particular person (or, more accurately, computer system) has conducted a particular search, and when, with an unmodified Computer Programming roll once they gain access to a system.
The Terran Empire datanet offers no anonymity; Imperial officials want total access to all user information if necessary for law enforcement or the suppression of dissent. It has no "anonymous forwarding" system or the like... at least not legally. Some jackers have established such systems, which they sell access to for large sums, and some systems outside the Empire allow this as well.