Responsible Handling of Billing Information?

moving on asks: "I've been asked by a client to build a fee based subscription service using surepay as the vendor for processing credit card transactions. Subscribers to the service will be billed X amount per month and that is the rub. Surepay does not offer recurring billing so I will need to store credit card numbers and related info. The question is then, how does one best do this in the most responsible manner?" The trick here is giving consumers the service they have come to expect from most websites, without exposing their personal information to would-be thieves. Do you think such a system is possible?

Comments

encryption

[paranoic]

Strong encryption and only connect the machine to any network (internal and external) when the bills have to go out. Filter all replies that don't come from the credit card responder.

Re:encryption

[Xzzy]

> and only connect the machine to any network
> (internal and external)

If you're unable to do this (due to staggered billing or something) the "next best" option is a heavily restricted network.

Give your machine with the personal information precisely one network connection and plug it into precisely one machine that can talk to the secured machine on precisely one port. Have your border firewall or equivalent drop any outgoing packets from either of these machines. Only let people do work on this machine from the console. Also use a straight cable between the machines.. ethernet port to ethernet port, crossover cable.

Then you have your webserver talk to the intermediate machine to handle transactions. Process submits authorization or billing request to intermediary, intermediary talks with the database, and issues a "yes" or "no" to the querying program. At some point you'll probably have to actually transmit user data to actually do the billing, so obviously everything in this chain will be encrypted.

Then install the best intrusion detection tools you can find/afford on all these machines and hire alert people to monitor logs. Treat any unexpected traffic as an attack and have someone walk over to your machines and physically unplug the machine from the intermediary until the situation can be identified/resolved.

This obviously assumes one believes that physical separation is important and effective, which I happen to do. ;) This also kinda relies on a security through obscurity standpoint, which contrary to popular belief can actually be useful as long as you don't let it lull you into complacency.

If server theft is a concern you'll also want to yank out floppy drives, physically secure the server somehow, look the bios, and if you absolutely require being able to copy data to this machine give it a read-only cdrom drive.

IMO, I wouldn't back up the server except for a hard drive image you can use to reinstall everything to a known state. Were I joe online shopper, I'd much rather re-enter cc info than worry that tapes were floating around the country with my data on it.

If you did even half of this, you'd have several times the level of safety than I've personally seen on some other online merchants, and I've been through a good number of data centers.

Re:encryption

[merlin_jim]

What about the storing of the credit information? That will most likely be coming in at arbitrary times, and thus the credit storage machine will need to be connected continuously.

Look at the guidelines in the Visa CISP. They have good information about this... the bottom line is: use asynchronous encryption (store your private key elsewhere and use it once-monthly to decrypt the data as you send it), use a firewall, and patch your OS often.

Amazon.com

[Anonymous Coward]

I remember hearing that Amazon.com originally used a Slackware box with extremely limited connectivity as a 'store' for the credit card info. Set it up with extremely limited connectivity, i.e. on a subnet unreachable by the world. Put only extremely limited services on it, i.e. set it up so there's a pipe for credit card info to get onto the box but nothing on the box is shared out and there's just one data path out from the box that sends an 'okay' signal that info verifies correctly. The machine should be set up so a zip drive is the only way to get info off of it, and you have to sit at the keyboard to do so.

Using GPG always appealed to me

[Anonymous Coward]

I always thought that this article described a way thats pretty simple, and easy to use / develop.
Cheers.

Hire the right experts.

[bluGill]

Bruce S. (I'm not gonna try to spell is last name) of Applied Cryptology fame is where I would start. Read his books, do a formal design of the system, and then hire him/his company to aduit your design BEFORE you start coding.

Don't forget to have a range of secure systems to work with. Run the web server on openBSD, and have the dataBase on trusted solaris. And use a good database and firewall (none come to mind off hand. (Note I'm giving examples, you can mix and match to please, just so long as they have to break several systems to get the data, none of which trust the others)

Take the additude that your web server will be cracked. Do your best to detect that. your firewall should protect the database (unless it is hacked!), and the database doesn't trust the firewall. With good detection you should shut down the front line systems before the cracker gets to the back end.

Remember to have experts aduit your design. Have other experts audit your code. (the later is hard, but it helps a lot)

Re:Lockbox, & let the customer decide...

[jayfoo2]

Actually.....

Even if they are not storing your credit card info for you to use again (i.e. a profile) they are almost definately storing the info for their own reasons.

The rationale behind this is that when there is a chargeback (when a customer tells their issuing bank a transaction is fraudulent or otherwise bad) the merchant is responsible for convincing the credit card company that it was a good transaction.

The problem is that when Visa and MC tell you that you have a chargeback all they give you is the Credit Card number, date, and amount. You need to have stored in your system the details of the transaction linked to that credit card number. Otherwise you can never fight chargebacks and you'll get screwed (for aboveboard merchants ~.4% of transactions result in chargebacks).

So it's unlikely that anyone who knows what they are doing would build a system that doesn't store your credit card data. Hopefully they are securing it well.....

Ditch Surepay...

[Brendan Byrd]

If they don't support recurring payments, maybe that's the initial problem. I guess your PHB doesn't like that idea, does he?

In terms of security/responsibility, it's impossible to create a 100% secure system, but as long as security is a focus in your software (and it isn't rushed), it's destined to be as secure as possible.

I guess I could list a few pointers to help you out, though (in random order):

• Don't trust HTML pages to give the correct limitations and forms. People can change local copies and send any data they want.
• Never use "secret" URLs, unless you use some sort of HTTP passwording system, or something else similar. (This has been the cause of many data-theft attacks.)
• Encourage customers to use secure passwords, such as 6+ characters, letter/number & upper/lower combos, no dictionary words, etc. (And for god's sake, let them use spaces, if they want.)
• Store billing information in a seperate system than the web server or any other system. Put the billing server behind the firewall on a private-class network. If one gets hacked, the billing data is safe.
• Make use of that 3-digit number on the back of CCs to verify that they aren't stealing numbers. (I really don't know if that's possible, but you should investigate it, as it would curb a lot of usage on stolen CC numbers, unless they have the physical card.)

NIH?

[hey!]

There's lots of issues with storing credit cards, not the least is showing that individuals working for you can't misuse the data and would have difficulty even colluding to misuse the data. I know, I was a IT director in the pre-dotcom days when people took these issues seriously.

Hopefully, there will be some insightful answers posted to /., but I think there are some other parties you may wish to ask. If you have a good CPA, they will know how this issue is handled in related businesses. Also, don't forget the credit card companies themselves, who should be willing to share their ideas for "best practices" when using their products. Remember, they have a vested interest in making their products convenient and safe for vendors to use.

Finally, this seems like a commodity sort of task that involves lots of headaches to get right (like payroll). Perhaps it would be better to buy the solution from a vendor/service beureau that can handle your requirements and so you can concentrate on the things which differentiate you. If,on the other hand, you are in the business of managing this kind of information you should have people on your team with considerable real world experience in this.

Good luck.

But it's still on the server

[A nonymous Coward]

If someone cracks the web server, then they also have access to the web server code which decrypts the database info.

If it's readable by the web server, then it's also readable by a cracked web server.

You really need the secret info on a separate machine, with the CC machine never regurgitating anything except a simple answer (valid / invalid) in response to the full set of info (CC#, expiration, name, address). The only info a cracked web server can get is answers to random info, and it would take too long for the cracked web server to try random possibilities.

Re:Why don't you ask a porn provider

[GigsVT]

Yeah ask CCBILL, they are secure, so they say.

Too bad /. rejected the CCBILL story, it's probably the biggest breach of security in recent years.

Re:Hashing

[pitcrew]

First of all the biggest risk is from internal theft. This can be handled by keeping the box secure both physically and from the internal/external network. Secondly the processor must get the data in a usable form thus it must be transmitted over the Internet as open text unless the processor has an encryption they want you to use. I solve this problem by sending the information to my card processor over dial-up lines. Yes it is slow, (1200 baud) but I can process 800 credit cards in about 45 minutes. The problem that I see for you is not the storage of the card info but the transmission over the Internet. You mignt want to look at ICVerify. This is piece of software that has been around for a long time and works fairly well. You can also process in real-time if you need to for sign-ups.

Re:Cart before the horse

[sharkey]

You may want to reconsider CCBill. Apparently, in March 2001, they were notified of an insecure CGI that exposed their merchants login information. They removed the CGI, but didn't tell their merchants, apparently hoping to sweep it under the rug.

SurePay is being discontinued

[Animats]

SurePay is on the way out. They've made a deal with Verisign to migrate users to the Verisign Managed Payment Gateway. The SurePay gateway is only being maintained for existing customers. It should not be used for new development.

Choose the payment software wisely

[phamlen]

1) As other people have mentioned, the biggest decision is which pay service to use in the first place. The wrong package will result in you:

implementing strong security on a system, which is difficult to do right

implementing a lot of customer service tools (to look up credit card numbers, issue refunds, track chargebacks, etc.)

generally spending more time than necessary in order to poorly implement something that another company has already done. Remember, the billing services are the ones who should be figuring out how to store credit cards, be secure, etc.

2) The place to look for payment systems is: here

3) Be sure to understand the Customer Service issue. It is quite reasonable to expect that Customer Service will ask to be able to "look at" Credit Card numbers, but consider carefully whether they need to see the Credit Card numbers or just search on the credit card numbers.

In my experience, you may end up spending more time writing the customer service interface than writing the customer interface - they may need to issue refunds to a card, they may need to investigate chargebacks (a BIG issue - especially with recurring charges.)

4) Avoid storing the credit cards if at all possible (but understand how you'll issue refunds and search for credit card numbers). As everyone states here, the security required in order to make this secure is easily weeks worth of effort. Again, picking the right payment service can eliminate this effort.

5) Remember, the client probably doesn't care about security enough to jeopardize payment - this is a clear case where the client probably wants his money more than he cares about preventing "potential attacks".

Not a simple problem

[geraldthewes]

I've build similar systems in the past. It's not a simple problem. In addition to a very robust and well thought network architecture and a very robust encryption architecture for the Credit Cards as mentionned in the previous posts you have to deal with:

Credit Card reconciliation - when you bill on a monthly basis, a lot of cards expire, are cancelled, this needs to be detected, the user informed the next time he tries to use the service, etc... There needs to be good adminstrative/financial metrics to track these.

You need very good operational interfaces and a strong underlying architecture so that people get billed when they should, and not when they should not. It's easy in cruise mode, but harder to keep track as financial processors or external connectivity is down, or after an upgrade, or system crash or other usual operational down-time.

Things get also quite complicated quickly if you offer multiple subscription services (monthly, yearly, first month free, etc...)

This stuff is hard to get 100% right (and it needs to be 100% right). I agree with the other post that recommend either a provider that already does that, or buying software that already does this.