Duke’s Buccaneers are a faction of Paranid who follow The Pirate Duke and seek glory by plunder. They have some history as mercenaries, but in X4 they are simple pirates. (You do have the option to turn them into a major power, as part of the Paranid story line.)

Unless you attack them regularly, the BUC ships are not hostile by default. They will, however, harass and attack your trade ships just like the SCA pirates.

They also object to being monitored. If you drop satellites in sectors containing BUC pirates, expect those satellites to get destroyed.

This is, effectively, impossible to prevent since BUC ships don’t start as hostile and can approach your satellite through any defenses (e.g. laser towers) you deploy, killing the satellite before becoming hostile and becoming targets for your defenses.

BUC ships can be captured like any other ship, and often have valuable quality ship-mod parts you can strip from them.

Completing missions given out by BUC stations will raise your reputation.