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Comment by rusk | Hacker News Reader

The key here being that he openly stored his PDA device in an empty foil “Twisties” bag.

Openly. Made no secret of his subterfuge. Maybe even boasted about it what a dope.

Apparently the manager didn't really care about the device in the bag. They knew about it and let it go.

However, they did care that he was not working when he said he did. They probably simply used the subterfuge as damning evidence.

Most employers I worked for would let me infringe some of their policies, as long as I was an otherwise good employee worth my salary.

Some other places were just totalitarian about their rules and I left because of it. They were probably happy they got rid of a bad apple without having to fire me. It's give and take really.

There's no point making it a secret, once someone looks at the GPS logs his would have gaping holes in the logs compared to other workmates. You can hide where you are, but you can't hide that you are hiding.

Well you can fake GPS coordinates but it's typically much more difficult.

Doesn't Android at least have a debugging option to fake location?

I just checked and I'm not getting a real GPS signal where I am. My position is being calculated based on cell towers and wifi networks around me. Two of our meeting rooms seem to be (an unhappy accident, most likely) shielded so that no cell networks are reachable.

It's hard to fake cell towers, but wi-fi signal is rather easy.

Most indoor locations have little or no GPS signal. I don't know the specifics of their tracking software or whether a chip bag would block GSM signals, but it's plausible that his GPS tracks just looked like he was working indoors.

You're assuming someone actually looks at them. They more than likely just get archived somewhere and are only looked at when there is a strong reason to, like work not being done. It's the sort of feature that sounds good to management that don't think about what they're actually going to do with the data. I'm sure many of us here have worked on similar reports the are just huge data dumps that no one ever looks at but management just had to have it for some reason.

I thought a Faraday cage had to be grounded.

No it doesn't. In practice they often are, but it's not necessary to block a signal from outside the cage.

grounding may be a safety issue.

That's one of the reasons. A charge can build up on the cage, but that shouldn't be a problem with small cage around a cellphone.

No idea, but it’s pretty widely known even in high school physics that radio waves can often be blocked or interfered with conductive metals such as aluminium foil, hence the “tin foil hat” jokes, and the plastic/rubber antenna lines or windows on smartphones with metal enclosures.

no? any charge structure completely surrounded by a conductor is indistinguishable from the outside. ground is an arbitrary reference.

From the article:

> Aluminum is not a great conductor—it heats up when a lot of power is pushed through it—so a snack bag would potentially melt if it was used to try to block a strong radio signal from inside. But the signals from GPS satellites are weak and can easily be interfered with, intentionally or not, in many ways.

I imagine that if the twisties bag had been grounded, it would be even more resistant to melting if the signal had been too strong for it.

What a load of nonsense. Aluminum is a great conductor of electricity. Not as good as copper, but good enough that it gets used as the conductor for high tension power transmission lines.

Additionally, you’d need a far more powerful radio than a cellphone would contain to melt a plastic bag. A cellphone radio is what, 3W? You might threaten the bag if you focused all that energy in a dime sized spot on the bag, but a cell radio is intentionally a roughly isotropic radiator.

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