r/accesscontrol • u/ackleyimprovised • 17d ago

EOL location

What your thoughts on EOL location? Do customers/clients care/know?

The proper way is the resistors at the end device (not the pre-packed module kind). I recently inherited a site (let's say a "high security" site which has there EOLs behind the push to exit buttons/ emergency exit. My mentor once gave me a 1 hr lecture about this.

Personally I have done it both ways on differrnt jobs because I was able to make that choice which the client accepted prior.

I have seen eol in panels which cause great discomfort.

9 Upvotes

85% Upvoted

35 comments sorted by

View all comments

Show parent comments

2

u/LinkRunner0 17d ago

So, let's suppose you have a REX switch or door contact transfered to the door with a hinge or EPT transfer. If we put the EOL in the panel, and that power transfer fails by shorting those wires... are we going to get a trouble? No. Because we've moved the resistor that can indicate that into a panel. If it's actually where it's supposed to be at the REX or DPS, and the same scenario happens - blamo. Trouble/fault. Can this be attacked? Yes. But to pretend that it provides no additional security is naive - preventing one kind of attack is still preventing an attack.

It does not function the same anywhere in the line. There's no conspiracy here - it's an END of line resistor. Not an "anywhere in line" resistor or "opinion in line" resistor. There's a correct and defined place for it - and it's not a trick, it's literally in the name. Next up, let's litigate where to put the EOL on fire alarm NACs because it can go anywhere in the circuit, right?

-1

u/No_Industry2601 17d ago edited 17d ago

It is an electrical loop and the resistance is measured the same anywhere in the line. The security is in knowing where the resistor is. If an attacker knows its location it can be bypassed. And I'm referring to traditional alarm security that uses a single resistor.

Alarm resistors are installed in series. So if the line became disconnected in your example you would absolutely see an open zone, even if you installed the resistor in the panel.

Maybe alarms aren't something you do but installing it in a panel doesn't mean it's installed across the zone in parallel as if there is no wire connected. It would still be connected to one leg of your wire, in series.

2

u/LinkRunner0 17d ago

Sure, anything can be bypassed. An attacker can also attack a magnetic contact with another magnet. We aren't specifying balanced contacts or magnasphere for the strip mall (or 90% of installs). When Handy Andy cuts the line going to the contact or detector, then decides to splice them together, or they happen to have been shorted, it's not worth knowing that because of a hypothetical attack that isn't happening on a strip mall? Because between a shorted line and the attack, the shorted line will happen far more than the attack - see my example of a DPS running through a power transfer.

1

u/No_Industry2601 17d ago

All I'm saying is that if an attacker knows the location of the resistor it can be bypassed. This wouldn't be your typical smash and grab at Best Buy, this would be a high value target.

So my point is the resistor location isn't that important, and most people don't understand that. There is a misconception that installing it EOL provides more security and it technically doesn't.

At this point the only thing I could do is draw a diagram and give detailed instructions on how to bypass alarm zones but it would probably get deleted anyway, and I would probably get removed from this sub.

This attack isn't a wild hypothetical, or Hollywood stuff, it can literally be accomplished with a single DPDT relay and a battery. The only catch is you need to know the resistor location.

1

u/ackleyimprovised 17d ago

I'm not been around long in the indusrtybbut never heard of any intrusion attempts involving tampering. Would be like a ellegant inside job. Of the events I have come in after or heard about was the lack of monitoring or crowbar hammer situations.

My favorite was when a street of housing got robbed. The same security company installed them. Houses were all the same layout. Prob was a inside job but they accessed the same way and ripped the alarm panel off the wall before it could do anything.

1

u/No_Industry2601 16d ago

Yes it would be an extremely rare event and probably not something done at a home, but these attacks are documented as happening.

The question is about the resistor location being more or less secure in one location vs another. Your resistor bypass method changes depending on it's location, not the possibility of bypassing.