This is a code word for a technique of mind control. These techniques were allegedly introduced to the US intelligence community and diverse secret societies when former Nazi scientists were brought to the country after WW II under the project Paperclip. These methods were further experimented with in the CIA MK Ultra and other projects. Most of the real activity is likely unknown to the public in any form.
The main idea of Greenbaum programming is artificially splitting the personality into dissociated alters, as is the case with naturally occurring multiple personality disorder. This is done with a combination of hypnosis and inflicting extreme trauma which splits the subject's mind into dissociated compartments.
Once the mind has been split, the compartments can be separately 'programmed' for performing various functions. The daily awareness of the victim is usually completely disconnected from the programming, The programming can be activated by various visual, auditory or other signals. Activating the program will give control of the body to a preprogrammed alter. This alter may have been programmed for carrying out assassinations, engaging in various criminal activities, espionage, prostitution etc.
Programming of this type may start spontaneously unraveling, in which case the subject can recover dissociated memories of programming. It is also possible that implanted programs get triggered by accident. The subjects are often programmed to self-destruct in such events. There is information on deprogramming former Greenbaum subjects but the information is not necessarily credible or accurate.
Since there is a high likelihood of validity for at least part of the information, it is to be expected that there is corresponding disinformation to counter this. Thus information on mind control should be viewed with this in mind.
It is possible that many reports of Satanic ritual abuse (SRA) and UFO abductions actually be planted false memories induced with a sort of mind control broadcast. The subject is very entangled.
See the Wave series at the Cassiopaea site for examples of mind control and its victims.