A Peek Inside a simple ATM Machine

by FocusHacks

In issue 21:4, I discussed the workings and "unofficial" reset method for LaGard ComboGard vault locks.  This time, I've got a whole ATM to work with.

The ATM I scored is a Diebold Cash Source Plus 100.  This is one of those smaller indoor ATMs that you would find inside a convenience store.  It features a monochrome LCD, eight option keys beside the screen, a number pad with four function keys (Shift, Cancel, Clear, and Enter) receipt printer, slots for one cash box and one "reject" box.  The card slot is a horizontal swipe-through under the screen.  There's a single five-tumbler lock on the front door.  Once opened, you're given access to three things: the combination dial, the vault door bolt control, and a pair of buttons that let you swing the top compartment upwards.

Once you squeeze the buttons together and swing the top compartment open, you're given access to the printer, the main power switch, the modem, and some Macintosh-style serial cables plugged into the backside of the LCD/keypad.  The printer uses standard thermal receipt paper, and there's only one printer, so there's no "live" paper audit trail.  I'd imagine it's stored in memory, but it may not keep an audit trail at all.  The modem in my ATM is a generic 33.6k serial modem.  When I power the unit on, it attempts to dial the mother ship, but I am not curious enough to hook it up to a phone line to see what happens.

Fig. 1: Inside the upper compartment

Of course, all the interesting stuff is held within the vault.  On my CSP-100, the vault lock was a LaGard 3332-3, which is a three-number (0-100) mechanical combination lock with wires that can be used for sensing bolt position and a "duress" combination.  These wires on my ATM were simply wire tied and unused.  A duress combination is the combination you dial in when you're being forced against your will to open the vault.  To activate duress mode, you dial in the combination normally, except the last digit, you dial to the "change" index, which is another mark about 20 degrees to the left of the "open" index.  This causes a plastic arm inside the lock to trigger the duress switch.

Fig. 2: Close-up of change index and open index marks

The duress wiring (white and blue wires) can be used in combination with a silent alarm or telephone dialer to notify the police or an alarm monitoring company.  The bolt position switch that I mentioned (red and black wires) operates in the same way, but is triggered whenever the lock is opened regardless of duress mode.  This can also be used with an alarm system or with a buzzer so that an audible alert is heard when the vault is opened.

Fig. 3: Lock case w/ change key, alarm wiring & boltwork

This lock can be easily replaced with one of many combination locks on the market, including electronic combination locks such as the LaGard ComboGard I wrote about in 21:4, Kaba Mas (or Mas Hamilton) Cencon S2000 or Auditcon.  The combination on the existing mechanical lock can also be changed, provided you have a change key, which my ATM came with, taped to the vault door.  Detailed combination changing instructions are available from LaGard.  I found them by Googling for: "change combination instructions group 2m."

Once the correct combination (or the duress combination) has been entered, the other knob will turn, which retracts the locking bolts that hold the door shut.  Once that knob is turned, the door opens, and you've got full access to the cash boxes, reject box, the main power supply, control board, combination lock housing (for changing the combination using a change key) and the conveyor belt that moves the money around.

The reject bin is where money goes that comes out of the cash box "out of spec," that is, multiple bills stuck together, comes out at an angle, folded, or damaged.  There are several kinds of cash boxes.  The one that came with my CSP-100 was a locking cash box that had a red/green tamper indicator on it.  The locks on my reject box and cash box were both operated by the same 7-pin cylinder key.  The tamper indicators will trigger at almost any sign of forced entry including simply removing them from the ATM.  The boxes can not be re-inserted when the indicator is red, and the key is needed in order to clear the indicator.

The ATM knows what kind of cash boxes are inserted by means of an array of buttons inside the ATM that are operated by plastic nubs on the back of the cash box.  I do not know what the coding is, but the reject box had its plastic nubs in a different pattern than the $20 cash box that my ATM came with.  Most cash boxes can hold upwards of 2,000 bills (2,500 if they're fresh, crisp, new bills), so a fully loaded cassette of $20 bills could store up to $50,000.  It's doubtful that you would see an ATM of this puny stature loaded with more than a few thousand dollars at any given time, though.

Pressing the small blue button on the lower front of the inside frame of the ATM allows allow you to firmly yank the innards out on a rolling rail system.  This gives you better access to the money conveyor belt system, the main system board, the sides of the cash box area, and the main power supply.

Fig. 4: Rails extended, electronics and cash handler visible

The vault is made of heavy gauge steel, which probably is the main reason that this thing is so heavy.  I certainly see why not very many ATM's get stolen.  They might look small and easy to manage, but you would need 2 or 3 men and a pickup truck to make a successful and timely getaway with this small ATM, and good luck getting the vault opened up.  It would certainly be more trouble than it's worth.

I have not even tried to get into the ATM's diagnostics or settings yet.  There are no power outlets in the storage unit I'm keeping the ATM in, so I'll have to move it somewhere else to continue tinkering beyond the mechanical realm.  Given the severe lack of external controls (and a user or installer manual), I am thinking that the setup/maintenance process needs to happen either over the on-board modem, or with an external device such as the ATM programmers I've found in the dumpster before.  I can't see where I'd hook such a device up, though.

That's the mechanical breakdown of a simple ATM.  As I experiment some more, look for another article on programming, setup, auditing, and diagnostics.