Pokémon Go API – A Closer Look at Automated Attacks

Tens of millions of people are out exploring the new world of Pokémon Go. It turns out that many of those users are not people at all, but automated agents, or bots. Game-playing bots are not a new phenomenon, but Pokémon Go offers some new use cases for bots. These bots have started interfering with everyone’s fun by overwhelming Pokémon Go servers with automated traffic. Pokémon Go is a perfect case study in how automated attacks and defenses work on mobile APIs. At Shape we deal with these types of attacks every day, so we thought we would take a closer look at what happened with the Pokémon Go API attacks.

Pokémon Go API Attack

Niantic recently published a blog post detailing the problems bots were creating through the generation of automated traffic, which actually hindered their Latin America launch. The chart included in the post depicts a significant spatial query traffic drop since Niantic rolled out countermeasures for the automation at 1pm PT 08/03. The automated traffic appears to have been about twice that of the traffic from real human players. No wonder Pokémon Go servers were heavily overloaded in recent weeks.

server_resourcesFigure 1. Spatial query traffic dropped more than 50% since Niantic started to block scrapers. Source: Niantic blog post

Getting to Know The Pokémon Bots

There are two types of Pokémon bots. The first type of bot automates regular gameplay and is a common offender on other gaming apps, automating activities such as walking around and catching Pokémon. Examples of such bots include MyGoBot and PokemonGo-Bot. But Pokémon Go has inspired the development of a new type of bot, called a Tracker or Mapper, which provides the location of Pokémon. These bots power Pokémon Go mapping services such as Pokevision and Go Radar.

How a Pokémon Go Bot Works

A mobile API bot is a program that mimics communication between a mobile app and its backend servers—in this case servers from Niantic. The bot simply tells the servers what actions are taken and consumes the server’s response.

Figure 2 shows a screenshot of a Pokémon Go map which marks nearby Pokémon within a 3-footstep range of a given location. To achieve this, the bot makers usually follow these steps:

  1. Reverse-engineer the communication protocol between the mobile app and the backend server. The bot maker plays the game, captures the communications between the app and its server, and deciphers the protocol format.
  2. Write a program to make series of “legitimate” requests to backend servers to take actions. In this case, getting locations of nearby Pokémon is a single request with a targeted GPS coordinate, without the real walk to the physical location. The challenge to the bot is to bypass a server’s detection and look like a real human.
  3. Provide related features such as integration with Google Maps, or include the bot’s own mapping functionality for the user.

pokemon-map.pngFigure 2. Screenshot of a Pokémon Go map

Mobile App Cracks and Defenses

Using Pokémon Go app as an example, let’s examine how a mobile app is cracked by reverse engineering to reveal its secrets. Since attackers mainly exploited Pokémon Go’s Android app, let’s focus on Android app cracks and defenses.

Reverse-Engineering the Protocol

The Pokémon Go app and the backend servers communicate using ProtoBuf over SSL. ProtoBuf defines the data format transferred on the network. For example, here is an excerpt of the ProtoBuf definition for player stats:

message PlayerStats {
  int32 level = 1;
  int64 experience = 2;
  int64 prev_level_xp = 3;
  int64 next_level_xp = 4;
  float km_walked = 5;
  int32 pokemons_encountered = 6;
  int32 unique_pokedex_entries = 7;
  ……
}

Pokémon Go was reverse-engineered and published online by POGOProtos within only two weeks. How did this happen so quickly? Initially, Niantic didn’t use certificate pinning.

Certificate pinning is a common approach used against Man-in-the-Middle attacks. In short, a mobile app only trusts server certificates which are embedded in the app itself. Without certificate pinning protection, an attacker can easily set up a proxy such as Mitmproxy or Fiddler, and install the certificate crafted by the attacker to her phone. Next she can configure her phone to route traffic through the proxy and sniff the traffic between the Pokémon Go app and the Niantic servers. There is actually a Pokémon Go-specific proxy tool that facilitates this called pokemon-go-mitm.

On July 31, Niantic made a big change on both its server and its Pokémon Go app. Pokémon Go 0.31.0 was released with certificate pinning protection. Unfortunately, the cat was out of the bag and the communication protocol was already publicly available on GitHub. In addition, implementing certificate pinning correctly is not always easy. In the later sections, we will cover some techniques commonly used by attackers to bypass certificate pinning.

APK Static Analysis

The Android application package (APK) is the package file format used by Android to install mobile apps. Android apps are primarily written in Java, and the Java code is compiled into dex format and built into an apk file. In addition, Android apps may also call shared libraries which are written in native code (Android NDK).

Dex files are known to be easily disassembled into SMALI languages, using tools such as Baksmali. Then tools such as dex2jar and jd-gui further decompile the dex file into Java code, which is easy to read. Using these techniques, attackers decompiled the Pokémon Go Android app (version 0.29.0 and 0.31.0) into Java code. The example code shown below implements certificate pinning from the com.nianticlabs.nia.network.NianticTrustManager class.

public void checkServerTrusted(X509Certificate[] chain, String authType) throws CertificateException {
  synchronized (this.callbackLock) {
    nativeCheckServerTrusted(chain, authType);
  }
}

When application source code is exposed, reverse engineering becomes a no-brainer. Pokemon Go Xposed used less than 100 lines of Java code to fool the Pokémon Go app into believing the certificate from the MITMProxy was the authentic certificate from Niantic.

How did Pokemon Go Xposed achieve this? Quite easily. The tool simply hooks to the call of the function checkServerTrusted mentioned in the above code snippet. The hook changes the first parameter of the function, chain, to the value of Niantic’s certificate. This means that no matter what unauthorized certificate the proxy uses, the Pokémon Go app is tricked into trusting the certificate.

There are many tools that can help make disassembly and static analysis by attackers more difficult. ProGuard and DexGuard are tools that apply obfuscation to Java code and dex files. Obfuscation makes the code difficult to read, even in decompiled form. Another approach is to use Android packers to encrypt the original classes.dex file of Android apps. The encrypted dex file is decrypted in memory at runtime, making static analysis extremely hard, if not impossible, for most attackers. Using a native library is another way to significantly increase the difficulty to reverse-engineer the app.

Reverse-Engineering the Native Library

The most interesting cat-and-mouse game between the pokemongodev hackers and Niantic was around the field named “Unknown6”, which was contained in the signature sent in the map request to get nearby Pokémon at a location. “Unknown6” is one of the unidentified fields in the reverse-engineered protobuf. Initially, it wouldn’t matter what value Unknown6 was given; Niantic servers just accepted it. Starting at 1pm PT on 08/03, all Pokémon Go bots suddenly could not find any Pokémon, which eventually resulted in the significant query drop in Figure 1.

The hackers then noticed the importance of the “Unknown6” field in the protocol, and initially suspected Unknown6 to be some kind of digest or HMAC to validate the integrity of the request. This triggered tremendous interest from the pokemongodev community and an “Unknown6” team was quickly formed to attempt to crack the mysterious field. The Discord channel went private due to the wide interest from coders and non-programmers, but a live update channel kept everybody updated on the progress of the cracking effort. After 3 days and 5 hours, in the afternoon of 08/06, the Unknown6 team claimed victory, releasing an updated Pokémon Go API that was once again able to retrieve nearby Pokémon.

While the technical writeup of the hack details has yet to be released, many relevant tools and technologies were mentioned on the forums and the live update. IDA-Pro from Hex-Rays is a professional tool that is able to disassemble the ARM code of a native library, and the new Hex-Rays decompiler can decompile a binary code file into a C-style format. These tools allow attackers to perform dynamic analysis, debugging the mobile app and its libraries at run time. Of course, even with such powerful tools, reverse-engineering a binary program is still extremely challenging. Without any intentional obfuscation, the disassembled or decompiled code is already hard to understand, and the code size is often huge. As an illustration of the complex and unpredictable work required, the live update channel and a subsequent interview described how the encryption function of “Unknown6” was identified within hours but the team spent an extensive amount of additional time analyzing another field named “Unknown22”, which turned out to be unrelated to Unknown6.

As a result, obfuscation still has many practical benefits for protecting native libraries. A high level of obfuscation in a binary may increase the difficulty of reverse-engineering by orders of magnitude. However, as illustrated by the many successful cracks of serial codes for Windows and Windows applications, motivated mobile crackers are often successful.

Server Side Protection

Server-side defenses work in a completely different way than client-side defenses. Here are some of the techniques used in the context of protecting Pokémon Go’s mobile API.

Rate limiting

Rate limiting is a common approach to try to stop, or at least slow down, automated traffic. In the early days, Pokémon scanners were able to send tens of requests per second, scan tens of cells, and find every Pokémon.

On 07/31, Niantic added rate limiting protections. If one account sent multiple map requests within ~5 seconds, Niantic’s servers would only accept the first request and drop the rest. Attackers reacted to these rate limits by: a) Adding a delay (5 seconds) between map requests from their scanning programs b) Using multiple accounts and multiple threads to bypass the rate limit

In the case of Pokémon Go, the use of rate-limiting just opened another battleground for automated attacks: automated account creation. They quickly discovered that while rate limiting is a fine basic technique to control automation from overly aggressive scrapers or novice attackers, it does not prevent advanced adversaries from getting automated requests through.

IP Blocking

Blocking IPs is a traditional technique used by standard network firewalls or Web Application Firewalls (WAFs) to drop requests from suspicious IPs. There are many databases that track IP reputation and firewalls and WAFs can retrieve such intelligence periodically.

In general, IP-based blocking is risky and ineffective. Blindly blocking an IP with a large volume of traffic may end up blocking the NAT of a university or corporation. Meanwhile, many Pokémon bots or scanners may use residential dynamic IP addresses. These IPs are shared by the customers of the ISPs, so banning an IP for a long time may block legitimate players.

Hosting services such as Amazon Web Services (AWS) and Digital Ocean are also sources for attackers to get virtual machines as well as fresh IPs. When attackers use stolen credit cards, they can even obtain these resources for free. However, legitimate users will never use hosting services to browse the web or play games, so blocking IPs from hosting services is a safe defense and is commonly used on server side. Niantic may decide to ban IPs from AWS according to this forum post.

Behavior Analysis

Behavior analysis is usually the last line of defense against advanced attackers that are able to bypass other defenses. Bots have very different behaviors compared to humans. For example, a real person cannot play the game 24×7, or catch 5 Pokémon in one second. While behavioral analysis sounds a promising approach, building an accurate detection system to handle the huge data volume like Pokémon Go isn’t an easy task.

Niantic just implemented a soft ban on cheaters who use GPS spoofing to “teleport” (i.e., suddenly moving at an impossibly fast speed). It was probably a “soft ban” because of false positives; families share accounts and GPS readings can be inaccurate, making some legitimate use cases seem like bots.

On around Aug 12 2016, Niantic posted a note on its website, and outlined that violation of its terms of service may result in a permanent ban on a Pokémon Go account. Multiple ban rules targeting bots were also disclosed unofficially. For example, the Pokemon over-catch rule bans accounts when they catch over a thousand Pokemon in a single day. In addition Niantic encourages legitimate players to report cheaters or inappropriate players.

In our experience, behavioral modeling-based detection can be extremely effective but is often technically or economically infeasible to build in-house. As Niantic commented in their blog post, “dealing with this issue also has opportunity cost. Developers have to spend time controlling this problem vs. building new features.” The bigger issue is that building technology to defend against dedicated, technically-savvy adversaries armed with botnets and other tools designed to bypass regular defenses, requires many highly specialized skillsets and a tremendous development effort.

The Game Isn’t Over

As Pokémon Go continues to be loved by players, the game between bot makers and Niantic will also continue. Defending against automated traffic represents a challenge not only for gaming but for all industries. Similar attack and defense activities are taking place across banking, airline, and retailer apps where the stakes are orders of magnitude higher than losing a few Snorlaxes. Bots and related attack tools aren’t fun and games for companies when their customers and users cannot access services because of unwanted automated traffic.

We’re back at Fluent this year!

A load of Shapers will be at O’Reilly’s Fluent Conference again this year and we’ll have a lot more in store than we did last year. Ariya and I (Jarrod) will be speaking, we’re sponsoring an event, and we’ll have a booth with (awesome!) prizes, JavaScript trivia, and demos of some really crazy technology. If you’re heading out to SF next week, make sure to look out for all of us and say hi:

At our booth we’ll be giving away a bunch of prizes that will allow you to make or control your own (benevolent) bots – Lego Mindstorms sets, remote control BB-8s, and arduino starter kits.

If you’re at all interested in working with JavaScript in ways you’ve never thought of before, we’re hiring a lot of new positions doing really fun stuff. If you’re curious, please reach out in advance so we can make sure to reserve some time. We really like talking about these things so just give us an excuse and we’ll make time for it.

Definitely make sure to check Ariya’s and my talks at the conference. I’m really excited to give the security talk and go over some of the insanity we get to work with at Shape.

From zero to hero: Toward frontend craftsmanship by Ariya Hidayat

ariyaAfter you have built a nice JavaScript application using Backbone, AngularJS, or React, written some unit tests, integrated a linter, and hooked up a continuous-build system, what should you do next? To reach the next level and create the highest-quality applications, you must first master a few more skills. Ariya Hidayat gives a step-by-step overview of adding code-coverage tracking and a dashboard, utilizing Git hooks to prevent regressions, leveraging Docker for a consistent development platform, and implementing cross-browser testing (including with evergreen browsers).

The Dark Side of Security by Jarrod Overson

jarrodAshley Madison data stolen… Twitch.tv breached, passwords need to be reset… 10 million passwords leaked! 13 million! 80 million!

What does this mean to you and your websites? You use secure passwords, your sites haven’t been compromised, and you have safeguards in place to protect your customers, so you don’t need to worry, right?

Right?

Jarrod Overson reveals the world where these passwords are traded, sold, verified, and used to exploit your sites. Even if you are diligent, doing everything you can to protect yourself and your users, you can’t protect against legitimate logins. So what can you do? Jarrod explains how you can start exploring how vulnerable you really are, how you might start recognizing malicious traffic, and what you can do to start taking a stand against your attackers.

See you at Fluent!

Avivah Litan at Gartner: Impact of Automated Attacks on B2C Websites

 

Avivah Litan, Gartner VP and distinguished analyst, is well known for covering big data analytics for cybersecurity & fraud as well as fraud detection & prevention solutions. In this educational webcast, she discusses automated website attacks and their impact on global business to consumer (B2C) brands.

Refer to this link to view the webcast.
Key highlights include:

  • How Gartner defines automated attacks on websites
  • How existing controls, such as device analytics, velocity checks, geolocation, and IP address whitelisting are defeated by attackers
  • How cybercriminals monetize their automated website attacks
  • And, most importantly, how to stop automated attacks

Imitation Game – The New Frontline of Security at QCon San Francisco

This week over 1400 software developers are gathering in San Francisco for QCon to share the latest innovations in the developers’ community. The conference highlights best practices in a wide range of emerging technology trends such as microservices, design thinking, and next generation security.

Below are three sessions that will inspire your thinking in next-gen web security and technology.


Wednesday Keynote: The Imitation Game – The New Frontline of Security, 9:00 am, Grand Ballroom, Shuman Ghosemajumder
As one of the four keynote speakers, Shuman Ghosemajumder, Shape’s VP of product management, will discuss the next wave of security challenges: telling the difference between humans and bots. From Blade Runner to Ex Machina, robots in sci-fi have become increasingly sophisticated and hard to distinguish from humans. How about in real life? How are bots taking advantage of user interfaces designed for humans? In his keynote on Wednesday, Shuman will explain how a complex bot ecosystem is now being used to breach applications thought to be secure.


Wednesday Track: The Dark Side of Security, 10:10 am, Bayview A/B, Nwokedi Idika
As Sun Tzu noted in The Art of War, “If you know the enemy and know yourself, you need not fear the result of a hundred battles.” To win the battle against rising cyber criminals, you must know your enemy. How do they think? What do they do before and after the compromise? How do they monetize? In this track, Dr. Nwokedi Idika, Senior Research Scientist at Shape, will guide you on a journey into the minds of the cyber criminals.


Wednesday Track: Javascript Everywhere, 10:10 am, Pacific LMNO, Jarrod Overson
JavaScript usage has been expanding past the browser for years. It’s now used in server applications at companies like Paypal and Walmart, native apps like Slack and Atom, mobile apps like Untappd, and even compilers for game engines like Unreal and Unity. Come to this track led by Jarrod Overson, Director of Software Engineering at Shape and JavaScript super fan, to learn why and how JavaScript is used everywhere.

Want more QCon inspirations? Follow #ShapeSecurity and #QConSF on twitter now.

Web Security Guide to Black Hat 2015

An important web security concept around “A Breach Anywhere is Breach Everywhere,” will be highlighted at Shape’s booth during Black Hat conference this week. Prominent attacks such as Uber account hijackings highlight how spilled credentials obtained from previous breaches can lead to account hijackings on another B2C site.

Make sure to check out Black Hat sessions relevant to escalating web security threats such as password cracking (Cracklord) as well as expanding web attack surface on technologies like EdgeHTML and Node.JS. You can also engage with web security anti-automation experts at the Shape Security booth #558. On Wednesday at 2:30 pm Shape will be hosting Ted Schlein, Partner at Kleiner Perkins (investor in ArcSight, Fortify, Mandiant), former CEO of Fortify and executive at Symantec.

Cracklord – A Friend of Credential Stuffers
If credential stuffing allows criminals to turn lead into gold, hash cracking is the act of digging lead from the Earth. Cracklord, a system designed to crack password hashes, will be explained by researchers from Crowe Horwath. As password cracking tools increase the pool of available credentials, B2C companies need to strengthen their web security defenses to defeat credential stuffing and account hijacking attacks.

New web attack surfaces revealed

Web attack surfaces are constantly expanding as new web technology frameworks and browser technologies continue to be developed and popularized. Those web frameworks offer both the opportunity for built-in security, as well as the risk of a vulnerability affecting the entire user base. In this year’s BlackHat, two briefings on EdgeHTML and Node.JS are particularly relevant.

Researchers from IBM will talk about new attack surfaces within Microsoft’s next generation rendering engine EdgeHTML (codename Project Spartan). Researchers from Checkmarx will talk about different attack methods on Node.JS as well. It’s important for B2C companies to be aware of these new vulnerabilities as attackers are likely to exploit them.

Stop by Shape’s booth #558
Stop by to engage with Shape’s anti-automation specialists to evaluate risks to your website and learn how to protect your web application and mobile API services. On Wednesday, you will get a chance to meet with Ted Schlein, Veteran VC at KPCB (investor in ArcSight, Fortify, Mandiant) and former CEO of Fortify and exec at Symantec.

Have fun and hope you enjoy your week at Black Hat!

Links for relevant sessions on web security


Please follow Shape Security on Twitter – #ShapeSecurity

3 Infosec Notes From Our Time At the MIT Sloan CIO Symposium

Last week, Shape Security attended the MIT Sloan CIO Symposium. Hundreds of CEOs, CIOs, and senior IT professionals from all over the world met to discuss the issues that keep them up at night.
Here we have distilled for you the three most captivating points discussed during the cybersecurity panel.
3. “We are approaching a cybersecurity perfect storm,” said George Wrenn, CSO of European electricity distribution leader Schneider Electric.
Wrenn believes the convergence of  “aging infrastructure, the interconnection of everything, the increasing sophistication of cybercriminals, and the unfixed security weaknesses of the early Internet age” leaves consumers and enterprises vulnerable to attack for the foreseeable future. Not only will it be difficult to address these issues individually, but it will be near impossible to survive a severe, multi-platform attack.
2. “No IT leader wants to stand in the way of innovation or customer satisfaction,” said Roland Cloutier, CSO of payroll services leader ADP
To prevent and survive future attacks, enterprises must shift their focus to mitigating risk over short-term rewards. Customer growth and user retention will only get a company so far if the danger of a breach is always looming. To combat this attitude, product and security leaders must lower risk tolerance across all departments and work together to establish a realistic baseline – for example, a threshold of affected users or records lost.
1. “Adversaries have better technology capabilities than security professionals do sometimes,” said Roland Cloutier, CSO of payroll services leader ADP
Today’s attackers are well-funded entities armed with thousand-node botnets, sophisticated malware, and an entire darknet economy willing to do anything for the right price. This leaves enterprises stuck implementing reactive security measures. The eventual worst-case scenario would be a major national attack that would spur enterprises, governments, and regulatory bodies to produce and enact new security standards. Although the situation would be devastating, the outcome could lead to better protections for consumers.
Take a look at the other events where Shape is attending, exhibiting, and presenting on our website: https://shapesecurity.com/events