I recently read a local story from San Antonio about how garage doors were activating near a NSA research facility. The NSA acknowledged an antenna was causing it, then interference stopped.

I am passionate about computer architecture and radio science, so here are my ideas. This is speculative because we cannot identify positively without RF samples to identify the mode, bandwidth and modulation rate. I cover the scientific concepts below.

Satellite images suggest this facility has capacity for ~10,000 servers/238 racks with the glycol chillers and multi-kW generators. The full parking lot indicates one wing is for research, because typical high-security data-centers would need less then 20 staff.

San Antonio is a great location for defense research as the city has over 30 D.o.D. cyber defense contractors and engineers with security clearance. Spying on CPU's at distance is actually a complex process of radio engineering, big data processing, and software/hardware deciphering.

The remote spy process is an interesting task for radio engineering experts:

Bombard a datacenter exterior with directional 300/400 MHz radiowaves, the same frequency as garage doors! The frequency is chosen based on penetration through walls , medium range, and frequency-stable high-power transmitters.

, medium range, and frequency-stable high-power transmitters. The radio waves hit a server, and when conductive metals resonate they emit harmonics from the original 300 MHz source signal.

from the original 300 MHz source signal. Harmonics for 300 MHz are at 600 MHz , 900 MHz , 1.2 GHz , 1.5 GHz etc.

CPUs naturally emit RF causing intermodulation to the spies harmonics which amplitude modulate (AM) frequencies at the sum and difference of every harmonic.

to the spies harmonics which frequencies at the sum and difference of every harmonic. You then record the harmonics with a receiver nearby capturing 300 MHz-2.4 GHz.

Harmonics over 2.7 GHz will be weaker, and won't leak easily. These frequencies have more of a " skin effect ". You capture them through cracks in a wall, or from flat surfaces like power conduits leaving a target facilities walls. Close proximity capture.

". You capture them through cracks in a wall, or from flat surfaces like power conduits leaving a target facilities walls. Close proximity capture. Finally, isolate the difference of recorded harmonics from the expected harmonics. From this point you have reliable noise fingerprint of a CPU from up to a half mile away!

Spying multiple servers/CPUs is possible because different objects exhibit different "time domains" by rule of "angular frequency" and "phase velocity". Metals differ based on conductivity, capacitance, resistance, length, size and even shape! You separate phase variance using a super computing cluster after recording the data.

The NSA already has knowledge from the TEMPEST project NSA-82-89, NACSIM 5000 to decode close-range radio signals into CPU values. The NSA has declassified many elements of the TEMPEST project.

Deciphering processor register values is not an automated process. You may need a team of 50+ PC hardware experts working for weeks on CPU registers producing x86 code equivalents to read CPU instructions and memory contents.

Still, a days worth of data could find passwords, encryption keys, IP addresses and sensitive data which can grant full remote access to a computer facility.

Spying could be prevented by creating narrow hallways/cavities around a datacenter and flooding with intense broadband RF noise, possibly metal-lined exterior walls, or building a faraday cage. All wiring would need RF filtering isolation. Broadband RF jamming is not safe for human staff without precautions, and large faraday cages are extremely expensive to build, install and maintain.

The NSA has been on a construction spree over the last several years. Funding for their projects is included in the Defense Department's unclassified appropriation bills, making datacenter locations and amount spent public record. Interesting the San Antonio location is not listed in the Defense Department's budgets appropriations at all, suggesting a higher security status.

It is exciting the NSA is possibly achieving the ability to read computers memory and state from a distance. It would be fantastic to get a software-defined-radio dump of these transmissions that were triggering garages for a true analysis.