Per 
General idea:
This SCP takes the form of a white noise machine which reprograms people who listen to it while they are asleep. Those who use it to sleep (the -1s) begin to seek out people who suffer from PTSD and try to get those people to talk about their traumatic experiences, usually with a level of skill in creating feelings of comfort and safety only seen in psychologists with decades of practice. Anyone who engages in such a conversation will become a -2. -2s will have their symptoms temporarily alleviated, but the symptoms inevitably return slightly worse, causing the -2 to seek out their -1 for further relief. This leads to the classic spiral of addiction. Importantly, neither -1s nor -2s are aware that their behavior is at all unusual. They believe that they are acting perfectly rationally, and in the case of -1s they believe they have always behaved this way. Most -1s eventually develop a group of -2s who are dependent upon them to maintain a normal life, and who support their -1, who eventually becomes unable to maintain employment or even a normal life because of constant demand from -2s. -1s at this stage appear unaffected by long periods without sleep or food, apparently drawing sustenance from consuming the traumatic memories of their "flock."
One -1 in particular (hereafter -3) is a notable exception. He is an electrical engineer who designs circuitry for semi-professional radios (mostly serious HAM enthusiasts, or small organizations that need to maintain communication in remote areas.) The -3 has been making small revisions to his own work since becoming infected, and a review of the radio circuits he designs shows that they have similar effects to SCP-XXX. This provides a route for SCP-XXX to reproduce. So far only one -3 has been identified. He denies any knowledge of the existence of SCP-XXX, and any intention of creating devices capable of reprogramming human minds; in fact, when SCP personnel suggested this he laughed and called the idea absurd.
Investigation of the circuitry designed by the -3 has yielded no conclusive results; they pass all industry tests and were nearly approved for production before intervention by SCP personnel. The current hypothesis is that the behavior of SCP-XXX emerges from poorly understood interference between digital and analog components in close proximity on the circuit board.
Irrespective of the mechanism, it's clear that SCP-XXX not only causes people to consume traumatic memories, but it also alters people so that they unknowingly recreate SCP-XXX when they are designing electronic acoustic systems. See also: Ken Thompson's "Reflections on Trusting Trust."
