I've developed an app that allows users to upload some photos and share them on Facebook/Dropbox/Twitter etc. Recently it went live in the app store.
However, I'm having a problem now: a bot is creating accounts and uploading many photos on my server. I've temporarily disabled the app, but now I'm looking for an efficient way to prevent this bot from doing this.
The bot's ip address is changing very often so it's impossible to block the ip. He creates accounts with a very realistic name and email address so it's hard to find out which users are real and which are created by the bot.
I was thinking of using a captcha, but I'm not sure if my app will be rejected by Apple if I implement this. I'm preferably looking for a way so I can prevent him from doing his work and so I don't have to resend the app to Apple again.
Could anyone give me some advice on what I could possibly do?
Thanks!
This is how I solved a similar problem:
I implemented a token-generator, which generates a one-time token for every single data transfer with the server, so even one for login-data, sending a file etc. This token is generated by a secret algorithm and can be verified server side, since you know how you generate one.
After one token is used, put it in a temporary list for the next X minutes/hours/days (depending on how many data transfers your server can handle). When a user tries to send data with a used token (i.e. the token matches one in the "banned" list), you can be sure that someone's trying to spam you -> mark the account as "spammer" and decide what you wish to do.
The algorithm must produce a different token each time (the best way would be a one-way hash), but you have to assure specific "properties", with which you can proof its authenticity.
So one very simple example:
Your algorithm in the client is generating a number between 1000000000000000000000 and 99999999999999999999999, this number is then multiplied with 12456564 and incremented by 20349.
The server becomes a specific command and data, and the generated token. Now it checks, whether (number - 20349)%12456564 is 0. If it's 0, it was likely generated by your "secret" algorithm.
It's a very basic example but you get the idea…
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I'm developing my first iPhone app to make what is effectively an app version of a fantasy league I created for work colleagues.
I am using Parse for the backend of the app. I only want people to be able to register with their work email address ie only if their e-mail address is _#mycompany.com
I'm sure this would be quite easy to someone who knew what htey were doing but I'm kind of new to this so any advice would be much appreciated.
Thanks
You could do this in a number of ways. The easiest way would be to have the validation happen on-device - just check the e-mail address the user has put into the app, and only allow the registration to happen if it matches the domain you want to limit it to.
However, although this is very easy it's also open to abuse and it's not very flexible (if you want to add additional domains, you have to update the app).
Fortunately, Parse offers cloud code, which lets you validate data server-side. Cloud code is written in JavaScript, and you then upload it to Parse. There is full documentation on Parse's website, including examples for validating data.
I have built a Custom B2B app for one of our clients. My question is how to automate the distribution of the redemption codes.
I have already looked at some of the MDM providers. Their solutions are too expensive and all we really need is a way to distribute the app from a webserver, not manage a bunch of mobile devices.
As you probably already know, when a client buys a Custom B2B app through the Apple VPP program, they get a spreadsheet with valid redemption codes for the number of licenses they have built. This spreadsheet has 2 columns: 1) redemption code 2) URL to redeem the code
I want to provide my client with a URL where they can send their users to download the app. They just don't have the expertise/infrastructure to distribute the app themselves. And emailing clients is not going to work.
I'm not a web guy, but it seems to me that we could write a webpage that would look at the spreadsheet for the next available activation code and then redirect the user to the associated URL. I'm not concerned with the number of licenses they distribute since I have another way of auditing the real number of users (Flurry). So I want this to be as painless as possible.
In fact, I have multiple clients and want to provide them each with their own URL for their clients. It seems like this shouldn't be too difficult to code.
The problem is, I'm not the guy to write that code. Any ideas on how best to do this?
Assuming that you don't want to show the user a website you should be able to do this with an online service like parse.com and the features it offers.
From a user POV you would supply them with a link which directed them to parse.com with a path and parameters indicating the action to be taken (get app) and what account is associated. This would redirect the users browser to the appropriate destination.
The main issue (and this applies to any solution) is knowing if the user actually followed through and used the code. i.e. should it be removed from the DB so it isn't offered to another user in future. Then you would update the DB each time you get a new spreadsheet.
Anyway, this could be achieved with a little javascript in parse.com, specifically, by using cloud code which can interrogate and modify the DB and then redirect the user.
Obviously if you need user authentication of some kind or other restrictions then you would need to start adding some web interface on top of this in order to collect the details.
I need to know if an installation has been paid for in the past so I can provide some premium features.
Storing a payment flag in indexeddb or the file system sounds easy to defeat. Periodically asking a server and caching the response could do the trick, but I guess the user would have to be logged-in at all times (through google or otherwise) and I'd rather not impose that restriction.
Maybe if there's a way to uniquely identify a user's machine (uuid, mac address, etc) that could allow me to determine if they've made that payment?
Ultimately, this is client side JavaScript. The only means by which you can prevent use of certain features, is to put them on your server and charge for the service.
Some weak methods for preventing access include license validation, and asking the server for non-essential information (if it was essential, then see the above).
For license validation, you could create an algorithm that takes data from the user and transforms it into something else. For example, say they create an account on your website, which your server knows is a 'pro' account. You could then take their first name and email address and do some magic on it.
Here's a simple example that takes those inputs and gives us a key. In this example if our first name is "John" and our email is "john#domain.org", then our key will be fcumnflqjpBfqockp0qtifcufLqjp. However, Tony, with the email "tony#doman.org" would recieve fcumnfvqp{Bfqockp0qtifcufVqp{
You can send this key to the user, and have your code decide whether it can extract the name and email by applying the reverse algorithm.
You can reverse the strings, do various bit math, etc. It's security by obscurity. Other than an account, this is the most common method. It's used by nearly all offline software. Its kryptonite is key generators, which reverse engineer your code, and generate keys by the algorithm you use to verify them.
All the methods such as uuid, mac address etc can be easily forged imo. I think you cannot escape keeping track of user's logged-in status. Implementing something like a cookie based mechanism would be the right way to go.
I currently have an iOS app that allows people to submit content to our server (twitter like). We don't have a login system, instead we rely on the UDID of the device to uniquely identify users (yes, aware that this isn't perfect but worth the tradeoff for users not having to create an account).
Requests from the iOS app are sent as POST requests to our server and are NOT authenticated in any way.
We are currently experiencing a lot of spam (obviously) and am looking for an easy method to verify that any request hitting our server in fact came from our app - and not some script that a spammer wrote.
We have tried using the user agent string which contains the app name but that is easily spoofed. Is there any way to verify that requests hitting our server is coming from our app?
One idea might be to include a random number as a parameter, and then encrypt that number with some private key. Have the server verify that the the encrypted version is = to the plain text version. (the private key would have to be on our server as well as embedded in the app).
I'm not looking for the perfect solution - a 90% solution thats easy to implement is def preferred.
Thanks!
I'd solve this by taking the message, salting it with a secret key known only to your app, and probably adding the username and UUID, then hashing them with a SHA-1. If the hash is presented along with the data, then it will act as a digital signature, and you can be reasonably sure that the message is authentic.
The shared secret key will have to be distributed with your app, so an extremely determined attacker will be able to reverse engineer it out of your app- but a casual spammer will be far more likely to just seek greener pastures.
Another approach would be to generate a pgp private / public key pair at registration- but this is a lot of work for this problem.
I have a web app that you can currently log into with either your email address or your username.
I'm developing an iPhone application and I'm just wondering if I should offer the ability to log in with your phone number. If this is the case, a user would first have to provide the service with a number on the web (an optional parameter).
I find it convenient on other services I use where I might not remember what email I have connected to it.
Is this a good idea?
Would you offer it in a service you were
building?
I'm trying to decide if its worth the trouble to build.
NOTE: This number would strictly be used for authentication.
I think that if your service is not about phone numbers (calling, texting, etc., e.g., whatsapp, etc.) I would not add phone number authentication for a few reasons:
Some users might be deterred to provide a phone number due to privacy concerns (no matter how hard you try to explain them that you will keep it safe)
With the phone number you will now have 3 options to login with, which is way too much. You want to keep your mobile login screen very simple
Some people may think that they might get SMSs from you or get their phone bill charged somehow
Overloads your backend
Just keep it simple...:)
To add to that, I personally prefer just email, without a user name. So many sites require user names AND impose restrictions on how this user name should be structured, so you end up with tons of them. With emails, you can't go so wrong - most people use a primary one to sign up for sites.
Hope that helps.