During the Sundering Era, between 530 AT and 900 AT, several cyborg communities escaped from the nanoplagues into the Oort cloud. Gradually they developed their own culture, the Backgrounder culture. Their view was that all intelligent species of sufficient technological power inside a crowded solar system would inevitably destroy themselves in a Technocalypse or similar disaster, so the only way of survival was to hide in the Oort cloud or interstellar space. They focused on getting rid of the wasteful biological parts that had to be kept hot, and instead became fully technological entities based on metal, diamond, ice and superconductor structures. They spread from icedwarf to icedwarf, converting them into habitats and moving them outwards. Their culture developed into paranoid isolationism - each habitat was independent and would keep its location secret from everyone else at all costs. To be known was to be vulnerable. Communications were set up by transponder buoys and elaborate cryptographic schemes, making communications slow and usually in the form of non-interactive propaganda/art transmissions.
As interstellar expansion began, the Backgrounders generally distrusted it. Many backgrounder habitats had begun to consider the advanced superturing and hyperturing AIs of the solar system not as saviours of humanity but as subtle tyrants balancing each other with threats of mutually assured destruction. Of course, their own nanotech AIs were beyond reproach. Transapientech advances like the conversion drive were just a ploy to divert attention. Still, some habitats decided it was safest to leave the solar system since with the drive, they might be vulnerable to attacks from the solar powers. Since then the Backgrounder culture has spread widely in its stealth habitats, always keeping to interstellar space and occasionally making forays into the outskirts of solar systems to grab resources. They do not take much part in interstellar civilisation and are generally viewed as little more than barbarians, but some cultures value their art, cryptography or low-temperature nanotech. There are also hints that they have stumbled on many odd discoveries out there.
Iceberg Cultures - Text by Anders Sandberg Cultures whose importance, size or power is not readily apparent to a given group of observers. For instance for most human nearbaseline observers the Silicon Generation, the Dry Empire and the Backgrounders were iceberg cultures, especially earlier in their histories.