What technical problems need to be solved to catch gold farmers?

Over in this thread, part of the discussion has been about whether Blizzard is really capable of catching/banning all the gold farmers and chooses not to (for whatever reasons), or if they really are doing what they can, and the farmers are managing to adapt and get around every attempt.

I’m not sure this thread is in the right place, but what I’m interested in is a discussion of how hard it actually is to catch this kind of behavior, from Blizzard’s position.

I believe it would be fairly easy, given the following assumptions (which may not be correct. I’m not a WoW player, so please correct me if I’m wrong)
[ul][li]Blizzard has knowledge of transfers. That is, there is no way to take money/goods that one character has and give it to another character without Blizzard being aware of it. I assume that some transfers are through an official auction interface, but even the ones that amount to one player dropping something on the ground and another picking it up are pretty simple to catch. Just track items from player to player.[/li][li]Blizzard has a reasonable idea of what different goods are worth. Going by auction houses and gold farmer websites, it should be fairly easy to assign reasonable estimates of value to items.[/li][li]Gold farmers need to make essentially unilateral transfers of value within game. It’s no good to them to make equal trades. They want to trade in-game value for real-world currency.[/li][li]Gold farmers will make all (or nearly all) of their transfers to customers and other people in the gold-farmer heirarchy.[/ul]Given the above, the simple algorithm is simply to map all the value transfers for all players for a little while, and anyone who has a strong net outflow of value is a likely gold farmer, and anyone they transfer to is a likely gold buyer. There are lots of minor adjustments that could make this more exact, but I’d be very surprised if any normal players exhibited this kind of transfer pattern.[/li]
Lots of people in the other thread seem to think this is a really hard problem, so what am I missing?

It’s not such a hard problem that Blizzard can’t track down the blatant sellers, and I don’t believe anyone said it was. In fact, thousands of seller/farmer accounts are banned regularly, probably using this exact kind of tracking.

However, if you can figure it out, so can the sellers, and there’s probably a few intelligent enough to figure out some kind of workaround. The reason why Blizzard or any other MMO company can’t catch them all is because at a certain level, the behavioral patterns of some farmers/sellers begin to overlap with the patterns of legitimate players. Try to cast too wide a net, and you’re going to catch some fish that didn’t need to be caught.

My wager is that the playerbase would rather tolerate having some farmers/sellers on the game than seeing even just a few legitimate players be banned. The outcry over that would be more than the outcry over farmers/sellers, and Blizzard knows it. It’s simply better to avoid hunting down every last seller and farmer and instead just take care of the blatant ones, because otherwise the false positive rate will be too high to be profitable.

Some of your assumptions are incorrect.


[ul][li]Blizzard has knowledge of transfers. That is, there is no way to take money/goods that one character has and give it to another character without Blizzard being aware of it. I assume that some transfers are through an official auction interface, but even the ones that amount to one player dropping something on the ground and another picking it up are pretty simple to catch. Just track items from player to player.[/li][/quote]
Blizzard does do this (though items cannot be placed on the ground as you state). The three possible vectors are: auction house, mail, or personal trade.

[li]Blizzard has a reasonable idea of what different goods are worth. Going by auction houses and gold farmer websites, it should be fairly easy to assign reasonable estimates of value to items.[/li][/quote]
Prices vary significantly depending on many variables, including

  • The age of the server (older servers have more money in the economy)
  • The number of players
  • The number of players in each faction
  • The number of people specifically farming for an item or in an area where said item drops
  • The number of people who already have an item
  • The number of rare recipes owned which may use said item as a component
  • What people are doing on the server (more raid guilds means higher prices on some items, lower prices on others).
  • What classes and levels people are
  • Players who (attempt to) monopolize the market. It’s not uncommon for someone to buy up all of X and then resell X for many times the original price.
  • Craftsmen and farmers who bomb the AH with tons of the same thing at once
  • Unusual spikes in demand or supply (i.e. holidays, patch changes, etc.)
  • Hundreds of other reasons

This can change overnight if a large guild transfers from one server to another!

Definitely items that go for thousands of gold could be reviewed but it would not be practical for small transactions. Besides which, there is nothing against the ToS for overpaying so they would not ban on those grounds alone.

[li]Gold farmers need to make essentially unilateral transfers of value within game. It’s no good to them to make equal trades. They want to trade in-game value for real-world currency.[/li][/quote]
This is true.

[li]Gold farmers will make all (or nearly all) of their transfers to customers and other people in the gold-farmer heirarchy.[/ul][/li][/quote]
Also true and how they are tracked. However, it is very difficult to automate I would imagine as there are several significant reasons for large cash transfers:

1 - Individuals sending gold to themselves for another character (many players have multiple accounts)
2 - Guild banks (which send valuable items/gold back and forth to characters frequently, and are typically level 1 characters)
3 - Legitimate trades of rare items. Purple (epic) items and rare recipes are not unlikely to sell for hundreds, and often thousands, of gold.
4 - Legitimate gifts - a powerful character may want to send their real life friend a lot of gold to get them started (there gets to be a point where tons and tons of gold doesn’t accomplish all that much)
5 - “Trust” transactions - someone sends me a large quantity of gold and I mail back an item independently. This is very common within guilds or among friends.

Keep in mind that it is not atypical for a player to mail dozens or hundreds of items in a single day! The auction house has a STAGGERING number of transactions, and I’m sure mail accounts for many times that.

It’s not simple. Sure, there are flags - I’m sure mailing a certain amount of gold flags your account for review - but there are legit reasons. It just takes awhile to track down and close the accounts - in that time they’ve already made their money on transactions and are working on other characters on other accounts for the inevitable ban, even though the gold is often removed from the economy. It’s time consuming, doubtlessly.

Maybe, but I’m not convinced. There’s a definite limit to the amount they can change their behavoir without a direct loss in income, because the behavior they’re looking for is what they have to do to get paid. If they really do change enough to hide in the noise of normal play, it’s pretty arguable that they’re not actually disrupting the economy anymore. They’re just playing and making trades.

The other reason I think they just can’t hide very well is that they are completely unable to hide the transactions.

Think of it like catching crime in the real world. The reason that illegal trade exists is because it’s possible to do exchanges that are not noticed by the authorities. How much would, say, illegal drug sales suffer if all payment had to be by check and all shipment had to be in clear plastic boxes through the US Postal service. 99+%, I’d bet. That’s effectively what the gold farmers have to deal with if Blizzard cares enough to actually look.

Before I address your points, what you’re discussing is millions of records and specific behaviors that MAY be associated with Gold Farming. Essentially, you’re discussing a pattern recognition / datamining problem (which is a large portion of what my thesis will be on, so I’ll get into that in a minute). There’s a lot of issues at work here, and considering the complexity of the issue at hand, I seriously doubt that it is possible to get 100% accuracy in classifying. So, for a moment, let’s assume your criteria are correct and analyze what could happen when they have a false classification.

This is a binary classification problem, so there’s 4 possibilities for a particular account. I’ll refer to the Ground Truth (what it ACTUALLY is) and the Prediction (what our classifier says). Thus, you’re accurate when your Prediction matches your Ground Truth, and you’re inaccurate when they don’t. However, there’s a big difference for the two possible errors. That is, if your Ground Truth is that the account is a Gold Farmer, but you classify as a legitimate player, then you leave one untouched; however, if the Ground Truth is that the account is legit, and you end up banning them because you think they’re a Gold Farmer… that’s REALLY bad. Thus, they have to favor the classification towards minimizing the latter, which generally results in an overall reduction in accuracy. However, you still going to have some errors, so you’re still going to have some Gold Farmers, but let’s see if we can get an idea of how accurate this sort of system would be:

Blizzard has knowledge of transfers. That is, there is no way to take money/goods that one character has and give it to another character without Blizzard being aware of it. I assume that some transfers are through an official auction interface, but even the ones that amount to one player dropping something on the ground and another picking it up are pretty simple to catch. Just track items from player to player.

Abosolutely, however, many Gold Transactions aren’t going to be 10,000 gold, they’re going to be smaller amounts like a few hundred. It’s not uncommon for friends and guildmates to give gold or high value items without consideration for the cost and without trading something in return. For instance, when I needed to buy my initial mount, my friend GAVE me 80g without me trading him anything in return. It COULD have been a trade for real life money, or it could have been a buddy who was sick of having to walk everywhere and wanted me to have a mount. Similarly, guilds work together to craft expensive items, so it’s entirely possibly that a high quality item is traded one way in order to benefit the guild. Or, even more confusingly, many guilds have “bank” characters. These are characters that are never played, but have all their bank and bag slots maxed out and are used to hold items for the guild’s general use, but so played characters don’t have to waste bank/bag space on items they don’t need themselves.

IOW, one-way transfers MAY be Gold Farmers, or they could be legitimate transactions.

Blizzard has a reasonable idea of what different goods are worth. Going by auction houses and gold farmer websites, it should be fairly easy to assign reasonable estimates of value to items.

This is true. However, this could lead you down a wrong path. Obviously, items that are worth more REAL money are more likely to be involved with Gold Farming; however, they’re worth more REAL money because they’re sought in the game. Thus, they’re also going to have more legitimate players going after them.

Gold farmers need to make essentially unilateral transfers of value within game. It’s no good to them to make equal trades. They want to trade in-game value for real-world currency.

This is true, to a degree. I don’t know how they work exactly, but I imagine the Gold Farmers have some sort of laundering process. That is, they have highly powered up characters that they use to earn gold, and they trade that gold away to less and less valuable accounts such that when they DO make a large unilateral trade, only the lesser accounts get banned. Its not uncommon that I’ve seen several of the same very rare high level item being sold in the auction house by a low level character.

However, like I mentioned above, it’s entirely possible that some fairly large unilateral gold transfers are legitimate actions. I would also imagine that when someone purchases a LOT of gold, they probably don’t send a single mail with 10,000 gold attached, they probably send several, from several different characters, to try and hide the transaction among more legitimate ones.

Gold farmers will make all (or nearly all) of their transfers to customers and other people in the gold-farmer heirarchy.

I don’t think I’m understanding this point. If you mean what I think you mean, then I imagine they do a large amount of laundering to distort the trading patterns and protect their accounts.

While this is intuitive, it’s not really that simple as I pointed out above. Anyone who get’s a mail with 10,000 gold attached from a single account, almost certainly that’s Gold purchase, but generally, I think the Gold Farmers are a lot smarter than that, and reduce their “shipments” into much smaller amounts. There’s going to be some people who just make and spend a LOT of money in a way that looks shady simply because they have a lot of time. Similarly, it’s not unlikely that an individual is really good at playing the Auction House, or making good deals, or has an exceptionally rare pattern, and can bring in a lot of gold in a way that looks shady.

What Blizzard REALLY needs to do is get someone develop some kind of classifier, which I imagine they already have, that takes into account as many of these sorts of tells as they can, but because of the high number of records, and their high dimensionality, you’re almost certainly not going to get 100% accuracy. And to run these reports, they have to use real time system resources, and use people to maintain and review these reports. This is why I imagine they tend to delete Gold Farmers in large chunks, because they run these sorts of reports on a periodic basis.

Well at least I didn’t spend as much time as I could have, typing up the same thing you just said. I previewed, saw you post and erased everything. :slight_smile:

One thing you didn’t mention was transferring gold between servers (which technically can’t happen, but does…sorta). If two players have characters on the same two servers, player A can give player B gold on one server and B can give A the same amount of gold on the second server. I’ve had guildies that are on 3 or 4 servers with me. When a guildie starts a character on a new server with me, we try to set the person up with enough money to make it easier.

Thank you for correcting them.

I suppose I should add another assumption: The majority of exchanges are between normal players. This lets Blizzard look at all the transfers in a given area/time slot/etc. and flag the outliers as suspicious. They don’t have to know what the price of an item should be. They just have to look for someone transfering an item and receiving far less than its average value in return.

They’re not banning for overpaying. They’re just using the overpaying as very strong evidence of some other ToS violation.

1 and 4 - Easy to filter out by doing a little social modeling of players. Transferring to one’s own character is pretty simple, since the same computers/locations/credit cards are associated with both accounts. Transferring to a friend is a little more difficult, but is still not hard. Most importantly, the player making the gift is likely to have a very normal pattern of behavior leading up to that for a long time. Someone who plays in a normal way, trading equal value between many others and then gives a gift does not fit the gold farmer model of someone who routinely makes unilateral gifts to many others.
2 - This sounds like it’s going to be a net zero change. The character does not produce goods and then give them away over and over. Not a gold farmer.
3 - But there’s still an exchange going on. A rare item for lots of gold isn’t suspicious. A rare item for very little gold or a lot of gold for a low-value item are suspicious, since the balance of transfers is always away from the farmer.
5 - Not a problem. The transaction doesn’t have to be even immediately. It just has to average out over time. A gold farmer will never get paid back.

In WoW, large guilds create “bank alts” to hold stuff (usually items), and is a legitimate action in game.

What you described above may also apply to a “bank alt”.

Need to be careful how you set your scan parameters.

This isn’t a fair analogy. Illegal drugs are illegal in ANY amount, no matter how small, and they’re distinctly detectable.

A better example would be if you’re mailing tons of money to a specific person for some illegal purpose (smuggling, a hit, blackmail, etc.), you don’t just send a suitcase full of 100’s. If you were laundering the money, you’d send it in many smaller installments, from many different addresses to many different addresses. These sorts of transactions would be extremely difficult to differentiate from legitimate ones, precisely because there’s countless legitimate transfers of money going on all the time.

That’s a little more complicated, but only if it’s a larger social network.

If two people are making trades between multiple accounts, it’s still pretty easy to map the value transfer, since all the accounts can be associated with a single player. The only way this would be tricky is if Player A had a friend B with two accounts on different servers, and you wanted to do some kind of A -> B, B -> C transfer with a third player, C on the other server. Even then, that essentially looks like a gift from A -> C, which isn’t that alarming unless A is constantly giving money away.

Not if the Feds have a database keeping track of every value transfer, no matter how small.

If they can look at their database and notice that one guy has given away huge amounts of money, pennies at a time, that’s just as suspicious as one who’s given it away in one chunk. Changing the transaction amounts won’t change the net outflow of money from a gold farmer’s account, and it’s the net values that are suspicious, not single large transfers.

Intuitively, it’s a simple problem, but in practice it isn’t. Datamining and Pattern Recognition are very difficult problems.

For instance, it’s perfectly legitimate to slightly over-pay the value of a specific item, right? Or at least slightly over pay the value and keep it within a non-suspicious range. Then, imagine this same character, who is slightly over paying does this to several other characters. Maybe he’s a legitimate player who doesn’t mind paying a little extra to guarantee he gets the items he wants. Certainly, how are you going to detect this? How can you be sure this “over paying” isn’t just due to fluctuations in the market.

For instance, last night I bought some materials I’d never bought before because they were for a new pattern I’d just obtained. I bought several of them from several different sellers. I had no idea what they were worth, it’s entirely possible that I over paid; in fact, it’s entirely possible that I over paid by a significant amount. A Gold Farmer could utilize a similar technique to transfer money off of his account to the less valuable accounts from which they actually have the point of sale.

Also, as fluiddruid pointed out, determining what is “over paying” is extremely difficult. I’ve seen the value of an item change by a large amount within a couple of hours. Similarly, they change depending on the time of day, day of the week (items tend to sell for more on Fridays and Saturdays), holidays, and even weather (our server is primarily East Coast players, so when weather is poor here, more players are online).

IME, predicting the price of a particular item in the Auction House is on the order of playing the stock market.

Similarly, I’ve also WAY underpaid (or sold items for well under what they’re worth). For instance, sometimes I get a nice item for a class I don’t play. I’ll try to sell it, it doesn’t sell, so I reduce the price and try again; but each time I try, it costs me money to list the item. Sometimes, an item that is worth a good amount of gold just doesn’t sell because no one really wants it, so my options are sell it to a vendor for a few gold, or sell it in the Auctions house for substantially less than it’s worth, but still a lot more than a vendor would pay for it.
Essentially, my point is that even with perfect information, you’re still going to have cases where legitimate players fit a certain profile (remember, these profiles can change VASTLY from server to server) and are flagged. Then Blizzard has to spend LOTS of resources to determine the validity of these flags. Even still, you’re neglecting the fact that you’re not only going to have errors where legit players are flagged, you’re also going to have errors where Gold Farmers aren’t.

#1 doesn’t seem kosher to me either, and should not be allowed. I wouldn’t want to play in a game where players do #2 and #4 without an in-character reason for it, but I can see how others would suspend their “roleplaying” experience in order to do this.

In the other thread, I posted that a simple solution would defeat this system–but I thought your proposal was far simpler than it is.

True, with a more complex system, Blizzard could be far more accurate in catching farmers. I wouldn’t be surprised if they have something like what you’re suggesting already in place. As others have suggested, though, tracking this is going to be a tremendously huge proposition. With six million players, many of whom make dozens of transactions a day, with different prices on different servers, with local fluctuations in markets, with plenty of valid nonequal trades happening, you pretty quickly get into a very complex algorithm to track these transactions. And all that algorithm will do is produce suspicious behavior, which requires manpower to examine. And when they succeed, farmers may find ways around the difficulty.
For example, they could set up an iteration of “buy low, sell high” tricks on an AH by which they could transfer money to a buyer (“Buy five stacks of linen and sell them at triple value. We’ll buy them from you. Buy ten stacks of silk with that profit and sell them at triple value. Another character will buy them. Use the profits to buy this rare weapon on the AH, which we’ll put up for sale; turn around and sell it for triple value. We’ll buy it.” and so on until you’ve transferred the appropriate amount of wealth). It would be pretty difficult for an algorithm to distinguish between this process and a legitimate auction house person.

Ultimately, I don’t think there is a magic bullet for catching farmers. Blizzard employs some freakin’ geniuses; if there were a magic bullet, I think we would’ve seen it.


Excellent point. Can you imagine how many people apply at Blizzard? I imagine they have the same kind of recruiting criteria that Google does and for the same reasons. In fact, I ALMOST applied to Blizzard myself after completely my MS in CS, but decided I should finish my PhD first and reconsider then. Sure, they have a lot of code jockeys who couldn’t solve this problem, but I can’t imagine that they don’t have PhDs (and others with the intelligence and experience) people working on precisely this problem.

Unless there’s some other reason for them not to. But speculation on that is more in the realm of the GD thread.

I agree that many many auction-house transactions of the type you mentioned would make this more difficult to prove, but I still think that the basic algorithm of looking at value flow is solid. In order to do the kind of transactions you mentioned, you’re going to have a large group of players that are tightly interconnected, trading with each other, etc., and the net value of that group is constantly going to flow out. Since these gold farmers don’t interact in normal gameplay ways with the vast majority of the population, it’s going to be pretty obvious once that analysis is done.

I agree that Blizzard could solve this if they wanted to. I’m sure they have plenty of people smarter than I in their employ. Personally, my guess is that if they really cracked down on gold farmers, then the Chinese gold factories would just switch to being mercenaries for hire (mentioned in the article as not currently financially viable). There is value to be extracted from the game, and no algorithm is going to trump economics.

Isn’t there another avenue of attack, too? The farmers have to hook up with their customers somehow. Can’t Blizzard representatives pose as buyers, and then sting the account that transfers the gold (and, of course, any accounts connected to it by these other patterns)?

This is starting to sound exactly like the drug war. We have been thinking about that for a long damn time and have not come up with a good answer.

The problem is, all these accounts that sell the gold are trial memberships. Unlike the drug war where they can actually arrest someone and take them off of the streets, if waste time trying to sting someone, they’ll just create another trial membership 30 minutes later.

It’s different in a number of ways. The main difference, I think, is that WoW is a controlled environment. As I mentioned above, how many drugs could really be sold if the Feds could track all the money changing hands?

The way to really beat this is to fight the economics: Make the cost of buying gold too high, in terms of risk. This doesn’t work well with drugs because the inelasticity of demand means that prices go up to compensate for the risk of the sellers. The demand for WoW gold would drop considerably if the buyers’ accounts started getting banned.