Schneier on Security
A blog covering security and security technology.
« Fourth Movie-Plot Threat Contest Winner |
| Software Problems with a Breath Alcohol Detector »
May 13, 2009
Using Surveillance Cameras to Detect Cashier Cheating
It's called "sweethearting": when cashiers pass free merchandise to friends. And some stores are using security cameras to detect it:
Mathematical algorithms embedded in the stores' new security system pick out sweethearting on their own. There's no need for a security guard watching banks of video monitors or reviewing hours of grainy footage. When the system thinks it's spotted evidence, it alerts management on a computer screen and offers up the footage.
Big Y's security system comes from a Cambridge, Mass.-based company called StopLift Inc. The technology works by scouring video pixels for various gestures and deciding whether they add up to a normal transaction at the register or not.
How good is it? My guess is that it's not very good, but this is an instance where that may be good enough. As long as there aren't a lot of false positives -- as long as a person can quickly review the suspect footage and dismiss it as a false positive -- the cost savings might be worth the expense.
Posted on May 13, 2009 at 7:55 AM
• 38 Comments
To receive these entries once a month by e-mail, sign up for the Crypto-Gram Newsletter.
Can't stores do this by tracking inventory and cash register balances? Sounds a lot less surveillance-state and a lot more effective than a computer trying to read my gestures.
Maybe it's cost-effective, though, because I don't know how much it costs to put either of these systems into production.
@anonymous - No, they can't. The whole point is to catch the cheats in the act so the store can stop the thefts, not just identify that it is happening in a given store. Whether there's one register or many how can tracking inventory or balances help identify when or who is stealing? There's no inventory transaction, nor monetary transaction, being recorded at the time of these thefts.
@Anonymous: In addition to what Markus said, tracking inventory is much easier said than done. Many stores shut down for days, to take inventory. For those that stock few but expensive items, it might be a one-evening job. For places that stock lots of items, though, even having RFID tags on them doesn't make it a fast process.
Apparently this is the same system that was reported last year to be testing use in airplane seat backs to look for sweating and nervousness in passengers faces trying to pick out the terrorist.
"The task grows much more complicated if you're trying to, say, spot the one hijacker among a plane full of innocent passengers.
Yet that is entirely possible, according to some researchers."
But I am curious if this system is tied into their registers and determine a missed ring by looking at the motion across the scanner to see if an item was actually registers.
Final test will be "friends eat free" program at MickeyD's.
Seems to me like it would be a lot easier to compare the amount of items a customer brings to the cash register (through video surveillance) and the amount of items the cashier actually registers(using a modern networked computer register).
Granted cheating employees could still register one cheaper item several times instead of the more expensive items, but I'm sure you could detect that in some way too.
Finished reading the article and got a kick out of this part too.
"For all of the complexity, Ferryman said the testing done so far leaves him confident that automated threat detectors will emerge - assuming regulations would prod airlines into paying extra for planes outfitted with the systems."
So what they are saying here is... as long as the government forces them to use the system, we will be able to sell our product. Would it not be better for them to create a product that actually works, and is efficient/cost effective enough that the airlines actually want to use it?
I read the attached article and came across this fairly over-the-top claim.
"My expectation is it's going to keep Chicago as safe as any big city can be in the U.S.," Orozco said.
Now, I'll go a bit off-topic, but at least within the referenced article.
I've actually been thinking about this a lot lately - in light of the differences in cities say like Detroit, Cleveland, Trenton and Pittsburgh. I would think city policies, working in conjunction with citizens and business community and the like have quite a lot to do with the overall safety of a city. As has been noted by Bruce at numerous times - we need to focus on the common issues as much if not more than the uncommon ones. It is far more common to be mugged or assaulted in a city, than it is to be attacked by a terrorist. At least in cities in the U.S. in Iraq perhaps the threats are different, in which case the mitigation tactics need also be different.
It'd be really difficult for a surveillance camera to detect exactly how many items there are.
Like clothing; a cashier grabs a pile of clothing and manually grabs each tag that's hanging down and scans each one, without actually separating the clothing. It'd be easy for the cashier to "miss" a tag and thus give a freebie to the customer, but hard for the camera to know exactly how many items there really are.
Or SD memory cards; it'd be easy to pick up 5 and only ring up 4, and it would be difficult for the camera to see how many are in hand.
Unless the cameras are really good quality cameras, I doubt it could accurately count unless the cashiers are ordered to move items across the scanner one at a time. Which may be appropriate for high priced items but not so good with smaller items.
The fact is, it doesn't even need to work very well, as long as the cashiers think it does.
For small store they often know who it is because the inventory disappear when a specific worker is on the shift but they need the camera to prove it.
For a big store I can see them spotting some behavior if they are connected to other sensor like the barcode scanner. the cash register and other camera. The camera only have to identify that an object passed in front of the scanner and see that nothing was registered as a cash transaction to send an alert.
What I find humorous is that Chicago is the hotbed of testing for these technologies. Let's get real here, if these don't work then the companies eventually go out of business, but if they do work, they also go out of business. That's because most of the positives are going to be the corrupt police officers and government officials, and Chicago can't allow any evidence of that now can they.
I remember watching a footage of suspected cashier theft over and over for nearly an hour. We couldn't determine exactly what happened. The cashier was too quick. Also as far as number of items rung up versus brought to counter, many stores use ICN's (inventory codes) to ring up an item. For instance, I can hit 20 to ring up a 30-pack of Busch or 22 and ring up a 12 pack. It gets even harder with bottles on camera, for instance someone could bring up a bottle of Remy Martin VSOP ($50) and if I were inclined to do so I could ring up a bottle of Remy Martin VS ($25). Employee theft is one of the hardest problems for a retailer. I doubt seriously any one automated system will catch it. The best defence is having several employees working nearby. If someone is cheating the system someone else will catch on eventually. I've seen several employees get caught stealing that way over the years.
I suspect it will be less reliable than a lie detector based on skin resistance or radiated energy.
But as Joe Ganley has observed,
"The fact is, it doesn't even need to work very well, as long as the cashiers think it does."
And that is the real danger as "little cashiers" into "mighty store managers" grow and with them their belife systems.
How long before a cashier is suspended or "work resourse realocated" (ie sacked) just because a read light comes on...
If they are going to put RFIDs in everything sweetharting and shoplifting can quite easily be dealt with i a simpler much more reliable way.
Which makes me think this technology will end up being used to "downsize" a workforce simply because a computer says so...
When are people going to wake up to this sort of stupidity (including Fast/Functional MRI as a lie detector when it cannot deal with left handed people or 20-25% of the population).
I had friends back in high school that worked at a grocery store. They did plenty of 'sweethearting'... but they didn't do it at the register. That would just be silly.
They instead worked with the inventory/stock guys. Anytime someone wanted something a 'bag of trash' was taken out back and thrown in or next to the dumpster. Someone would go by later and pick their order from the back of the store.
Whole lotta good cameras in the front would do for that store :)
This is actually, I believe, the main reason for having the goons at the door checking receipts. It's not to keep the customers from taking merch and walking thru the checkout line (that the goons just saw them do) and out, it's to catch their own cashiers under-ringing (either on purpose or intentionally)
Here's something to look for the next time you visit a store with a stop-loss goon at the door:
Do they even look at your friend who isn't holding a store-marked bag?
Some friends and I have noticed this at the local Big Box Electronics Place. We've never tried to actually exploit it, but it would seem they believe nothing that hasn't been past the register can walk out the door.
re: Stop Loss Goons
I've seen three versions of SLGs.
Version 1 at WallyWorld they stop you if you have something under your cart or something in your cart that's not in a bag. They'll ask for your slip and glance it over to make sure the noticed item is actually on your slip. I can understand the under-the-cart thing. I've actually had stuff under the cart that I forgot to put on the belt. Makes a modicum of sense.
Version 2 at WallyWorld - you've got a cart mounded high with bags, nothing underneath, plus 2 or 3 bags in each hand. The SLG stops you at the door to ask for your receipt that's already tucked away in your wallet. Once wrestled out, they glance at the receipt and say "Thank you" WITHOUT EVEN LOOKING AT THE $%#@ING CART! WTF? Did you just want to see me wrestle with the bags to get the receipt out? Oh, and by the by, what about the 4 people who walked out around us that YOU DIDN'T STOP! Is it just me that looks hinky or what?
At Costco they look at your slip and actually *COUNT* the items in your cart to make sure it matches the count of items on the slip. Granted, they don't usually try to match items up, so 4 packs of hamburger and 1 book could also be 3 packs of hamburger, 1 book, and 1 DVD.
What "C" mentions, is why trash bags in most offices and stores are now clear: it makes hiding "loot" a lot harder, and makes it much harder to haul out back.
If you're in most modern supermarkets in the US, you may notice that the combined scale/scanner has an upwards facing red/green light. The green light flashes on a good scan, and the red light flashes on a bad scan. There will be a different beep/bloop depending on good/bad scan. The upward facing light is for the security scanner overhead in the ceiling tiles. Next time you're at a large supermarket, look up.
Curious thing is, you are not required to submit to those SLGs. I've done it a number of times. Especially when my (multiple) carts are overloaded, and I'm shopping with the kids.
I just say "No thank you. I don't need this service." AND KEEP WALKING!
I've already paid for everything. It's mine. I'm not required let anyone else handle or examine it.
It is, perhaps, rude on my part. But so is asking to examine a 1 meter long receipt while the kids are screaming.
It also says something about us as a society that so many of us will blindly permit arbitrary individuals such power without ever questioning it.
Imagine what a dishonest con-man could do...
Soon we will be watched by our robot over-lords. :-)
If the humans manning the security cameras in Vegas casinos have trouble spotting cheats, I doubt that such software would be much of an improvement. Sleight of hand usually wins such contests.
@ C, Peter,
"it makes hiding "loot" a lot harder, and makes it much harder to haul out back."
The old "rubbish out back" trick still works it just depends on who is involved and what the pay off is. Groceries are nickles and dimes, a half dozen bottles of spirits is not (at least in the UK where the duty is more than 80% of retail)...
You may have noticed that some larger stores have a rubbish compactor usually around back on the downwind side of the store, often inside a fenced off area with gates on the store side and gates on the street side for the truck to pick up the compacted load.
Now have you passed the store after clossing and noticed that often not all the trash ends up in the compactor, in these modern "recycle" times often there are separate areas for plastic wrap and cardboard.
Often the store cages used to hold the plastic etc are not changed much since being filled and taken from the shop floor.
Well as some customers will have seen on a busy floor often the rubish gets put ontop of stock just to keep the number of cages in an area down.
This sort of accidental cover up of signed out stock happens more often that you would think.
Now if there is only one bottle or two at the bottom the chances are that nobody will either check or care as it makes it's way through the store as the packaging rubbish cage.
If it does get picked up then it is usually put down to being just an accident as store rules usually prevent floor workers getting the stuff out...
Now if you are working the compactor or the recycle sort you are likley to be a kid on minimum wages etc. If you thought of a plan to get the stuff out then would you worry about getting caught?
The main deterant is CCTV cameras, however if you cannot work out how to shield what you are doing from then then you should not consider it as you will get caught. Also you need to watch out for colleagues who will grass you up, but being "part time" "rubbish staff" generally means you are shuned by regular staff, and being quiet and shy generaly gets you left alone at a job nobody else wants to do.
However a couple of individuals working on rubbish with a floor assistant can get 20-30 bottles out a week if they shift it on for 50% of retail then they are not doing too bad on a bonus (200-300GBP/week) split three ways.
However there are other tricks involving switching entire cages of booze back into the delivery lorry (that also picks up the recycling)...
Where people see "easy money" there is usually someone smart enough to exploit it. The only advantage most store "managers"/"detectives" have is they have seen it all before (or think they have).
But as my father quite reasonably pointed out when I was young,
"If you are smart enough to commit a crime and get away with it you are more than smart enough to earn more money honestly".
And after a life time of looking and evaluating as far as I can see his reasoning was right nearly every time.
Here's an idea for drive-thrus. Detect when the window has opened but no sale has been rung up. Then show the suspect footage to someone.
We used to do something like this at Dairy Queen when I was a kid. We'd get a cone, give our friend behind the counter a five, and get four ones and a dollar in change in return.
The boss was none the wiser and we got free ice cream. Yum!
When can we get these installed in the congressional chambers?
Fascinating system shows employees and customers on video, plus cash register; on the same screen, you see what the cashier rings up, and whatever alerts supervisors want, i.e. how long the till stays open. More on this at Thiefhunters in Paradise: http://bobarno.com/thiefhunters/2008/06/...
RFID chips are too expensive to be used for all purposes at this time, but they are cheap enough to be used for inside theft prevention services when that is a problem.
You RFID one in a hundred items and view the tape when one of those items goes through a register area without showing up on a register sku record.
"The fact is, it doesn't even need to work very well, as long as the cashiers think it does."
That won't last. Cashiers make mistakes. Sometimes they know when they make a mistake and they just let it slide anyway because life's too short, its the end of the shift and they are too tired to make the effort.
Have that happen once or twice to a couple of cashiers and pretty soon the entire staff will know that the system is unreliable at best.
Real life nightmare scenario: working with a major retailer, we implemented a high quality video surveillance system with good zoom capabilities. Sounds good so far?
The video was easily capable of picking out the numbers on a credit card, including the CSC on the back when the card was turned over to inspect the signature.
The result? Either the camera system had to be crippled sufficiently to prevent exactly the kind of clear image it was installed to deliver, OR the entire camera system had to comply with expensive PCI (Payment Card Industry) secure data management practices!
Predictably, the ability of the expensive new high quality cameras to zoom was inhibited. In software.
When I was in college, the system in fast food was something like this:
"Hey, here's a Coke, it makes you look like a customer if the boss comes in."
"Hey, don't you know about our new deal? Get a free Burrito with every free Coke."
gee, I don't know WHY that place went out of business.
The real killer would be to combine "sweethearting" with "UPC switching".
The staff can let you know which products are the best deal and easiest to work on the switch - similar packaging, for example, would make UPC switching work better. You bring in only the codes you need, apply them to products discreetly, and then head for your friend's checkout. They check you out "without noticing" that you got the tub of something expensive but the cash rang up the tub of something cheap.
Then, when you go looking for sweethearting, you see each one item on camera, each one item scanned, and each one item paid for, and everything looks good. It won't be until the next time you do inventory that you find the mismatch. What you can't detect on camera is when your employee has turned off their "UPC switch detector" - something that rarely goes off anyway, because it doesn't happen on every transaction.
This will only be catchable on an automated basis when the security cameras are good enough to do automated product identification from a distance.
This might not be too hard a machine vision problem because the motions are so stereotyped, and also the gross motions are largely confined to one plane.
It could be subverted if you could play with the system and learn the right gestures. But cashiers don't have the opportunity, and
as stated, the psychological effect and
useful filtering probably suffice to make it
Employers who are that worried about employee skulduggery should try (a) paying a decent wage, and (b) doing some real management of their employees and their stores rather than relying on absentee high-tech surveillance.
Employees who hate their jobs, their supervisors and their employers will always be motivated to conduct rip offs. People who feel appreciated, trusted, and well-compensated, and who see their management walking around setting a good example, won't.
This is not a technical problem.
I admit to doing this for friends while I was at college. I can't see this system working without creating a lot of false positives; I just used to turn the product slightly so the barcode wasn't read as I swiped it across towards the bagging area.
Thinking about it, a more accurate system would be detecting products moving across in front of the cashier, where the barcode scanner is, and then alerting someone when there's no corresponding barcode scanner read.
A lot of people are mentioning having a system that detects things moving in front of a register but not ringing something through. This however, wont work. You would have so many false positives that you'd be just as well off as if you watched every transaction. There are a ton of times that you have to swipe an item two or three times while switching angles and sides to get the barcode. Your system would see this as one rung up item and two stolen ones. Also what about items that you purposefully don't want to scan? Say items with the BC up top which you've already scanned with a hand scanner.
Really there's no substitute for a good Assets Protection team.
@Dave - I worked for three years for the world's largest inventory service and we only had one chain store client in my district that closed for inventory and a couple smaller local stores. Most stores perform inventory late at night or early in the morning. Most big box stores (K-Mart or Home Depot as examples) would perform counts starting in the early morning and continuing through the day. When the store received their final results it would look at sales time stamps verses the inventory time stamps to deduct the items sold after a particular area was counted.
Very few stores require 100% accuracy (mostly jewelry stores). There is a certain margin of error that is expected (say 1-2%). It was far more common for one type of product, say cd/dvd's or jewelry to be 100%. One client was quite upset that we undercounted their estimated inventory by about a half million dollars (the missing stock was just not there). Grocery stores are counted financial, just the price and quantity of items.
Finally, it is a labor-intensive process. While I could run a jewelry store with five people and be done in three hours, one department store client required more than 200 people to be finished in less than six, another took 40 people and two days (about 16 hours in store). But at no time did any client we have, or our major competitor, require being shut down for days.
I am a cashier who has been accused of "sweethearting" because apparently some items were voided off the tickets. I did not do this. Is there some computer glitch that could have made this happen? I am waiting to hear what sort of disciplinary action will be taken against me. I did nothing wrong, I have nothing to hide, and I am telling the truth. Two of the occurences happened on the same day at the same register, which to me is suspect. Anybody know of an answer?
Schneier.com is a personal website. Opinions expressed are not necessarily those of BT.