Nano-rot is not the result of any particular nanotech device, but is instead a general phenomenon, and a property of any highly evolved mechosystem. The term is used to refer to the action of any artificial organism that employs nanotech, is capable of self-replication, and breaks down natural or synthetic materials as part of its life cycle. Agents of nano-rot may be simple nanobots, but these often lack sufficient flexibility to survive and replicate in complicated environments. More often nano-rot is caused by microscopic bots that employ nanoscale technology as a part of their internal processes. These may be dry nano, synano, or bionano in origin, or they may even be highly gengineered descendants of natural organisms (Terragen or otherwise). They are the artificial equivalent of the bacteria and fungi that are an essential part of any ecosystem. Usually these bots were specifically designed to have a function as decomposers, as part of a mechosystem's recycling systems. However some agents of nano-rot were originally designed to be part of some limited manufacturing or extraction process and others yet again were created as agents of destruction by military or terrorist organizations, and have escaped from their original context or have been purposely adapted to other uses.
Good system design employs nano-rot, just as good ecosystem design takes advantage of the action of decomposing organisms. However, escaped or poorly managed nano-rot can be a nuisance or even a life-threatening hazard. In vecs or bots they may even be equivalent to some of the diseases that afflict biological organisms. Important structures or subsystems may be weakened, malfunction, or collapse as a result of nano-rot. On the other hand they may simply become unsightly and acquire a "rusty" or "moth-eaten" appearance. In a standard Terragen oxygen-bearing atmosphere structures made of metals or diamondoid are particularly vulnerable, since nano-rot can live and replicate by converting them to metal oxides or carbon dioxide and using the energy released in the process to create more copies of themselves. Unchecked, such a process can consume entire cities or megastructures. Primitive rogue nano-rot agents, poorly controlled due to an even more primitive understanding of their ecology, are believed to have been a major element in the famed nanodisaster early in Terragen history. There have of course been major outbreaks of nano-rot "organisms" in the times since, but a more fundamental fact is the fact that decay and decomposition have been a significant part of the technological landscape ever since; artificial substances from plastics to diamondoid to steel are as subject to decay as natural ones always were. For this reason, some builders prefer to use inert materials, while others inoculate their structures with protective nano.
Nano-rot is often one of the more unwelcome constituents of an infestation of krek, making the removal of that unsavory and insanitary material an even higher priority.
Sophont-level mechosystem designers and managers find the management of nano-rot bots a significant challenge, and even transapients may be surprised on occasion. Not only are the interactions of a well developed mechosystem fully as complex as those of any ecosystem, but new nano-rot agents are often introduced by or modified by sapient or transapient individuals whose actions may themselves be unpredictable. What is more, existing nanorot bots may evolve, either through natural selection or as a program integral to their design, or in some combination of the two.
In most polities quarantine restrictions for nanobots, microbots and other m-life are just as comprehensive as those for biological life forms, and the creation of any self-replicating bots is subject to heavy regulation, comparable to the creation and introduction of new self-replicating biological organisms into the ecosystem. Recently there have been several unfortunate incidents involving the careless introduction of microbots based on designs derived from studies at Stanislaw. Some of these bot forms have proved to be as aggressive as they are sophisticated. As a result many polities have placed a moratorium on Stanislaw-derived bot designs.