Malicious Xcode could spread via download manager Xunlei

What’s at stake?

We reported last week that popular Chinese iOS apps were compromised in an unprecedented malware attack. We discovered that the source of the infection was compromised copies of Xcode hosted on Baidu Pan. Apple has published an article urging developers to download Xcode directly from the Mac App Store, or from the Apple Developer website and validate signatures. We’ve now discovered that even if a developer uses a download link seemingly from Apple, he might still be possible to obtain a compromised copy of Xcode.

Please note that we do not have evidence that such attacks has happened. But it is an easy attack that anyone can implement.

How does it work?

This compromise happened because of Xunlei. Xunlei is the most popular download manager in China. Much of its popularity is due to the fact they can accelerate download speeds by pulling resources from other Xunlei users as well as cached copies on the Xunlei server. All of this, however, is invisible to users. Users can simply enter a regular http download address into Xunlei  download manager and the download will start. Chinese developers were using direct download addresses such as to download Xcode.

Because of Xunlei’s P2P and server cache, download speeds would be much faster than the Mac App Store. Downloading via Xunlei also means that developers do not need to be enrolled in the Apple developer program. Direct downloads of Xcode via the developer program cost $99. Because the URL belongs to Apple, users were tricked into thinking that the download link was authentic and hence the Xcode copy. But in actual fact, the file is not authentic because it comes from Xunlei’s P2P and server cache.

The way to “host” a compromised copy of Xcode on Apple’s server is to trick Xunlei locally and let the error propagate. For example, a malicious user can hijack locally via host file and download from a non-exsistant URL Xunlei will then correlate this URL with the file specified by the malicious user and provide this file to other innocent users.

This is what actually happens when you use Xunlei to download

But if you look at the details of the download source, you can see that 0% of the download is from the original server (i.e while the server cache accounts for 26% and P2P accounts for 3% of the download.

You can also see that attempts by Xunlei to connect to were redirected to  because Apple only allows users in the Apple developer program to access the page.

Malicious attackers can poison Xunlei with a URL similar to a real Apple Xcode URL and then post the fake URL on forums and download sites. Most Chinese users by default use Xunlei to download. In fact, they have to if they are not enrolled in the Apple developer program. Most will have a compromised copy of Xcode, seemingly downloaded from Apple.


What can developers do to prevent future attacks?

Our suggestions are exactly the same from our last blog post.

  • Always download Xcode from the official Mac App Store. For other developer tools, always download these from official sources.

  • Always check the digital signature of developer tools. It is irresponsible for developers to ignore signature warnings. Xcode clearly should have been signed by Apple; all other versions should have produced user warnings.

  • Separate your development system with your everyday system. Development systems should be used solely for development and not for browsing random sites. If physical separation presents too much of a problem for developers, at the very least, a dedicated user account for development should be used.


Xunlei users should be cautious

As demonstrated above, Xunlei cannot be trusted to download the correct file, even if the download link is HTTPS. Users should manually check hash after download or use the browser’s download function.






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星期一, 8月 03, 2020

Announcing the Release of GreatFire Appmaker

GreatFire (, a China-focused censorship monitoring organization, is proud to announce that we have developed and released a new anti-censorship tool that will enable any blocked media outlet, blogger, human rights group, or civil society organization to evade censors and get their content onto the phones of millions of readers and supporters in China and other countries that censor the Internet.

GreatFire has built an Android mobile app creator, called “GreatFire AppMaker”, that can be used by organizations to unblock their content for users in China and other countries. Organizations can visit a website ( which will compile an app that is branded with the organization’s own logo and will feature their own, formerly blocked content. The app will also contain a special, censorship-circumventing web browser so that users can access the uncensored World Wide Web. The apps will use multiple strategies, including machine learning, to evade advanced censorship tactics employed by the Chinese authorities.  This project will work equally well in other countries that have China-like censorship restrictions. For both organizations and end users, the apps will be free, fast, and extremely easy to use.

This project was inspired by China-based GreatFire’s first-hand experience with our own FreeBrowser app ( and desire to help small NGOs who may not have the in-house expertise to circumvent Chinese censorship. GreatFire’s anti-censorship tools have worked in China when others do not. FreeBrowser directs Chinese internet users to normally censored stories from the app’s start page (

星期五, 7月 24, 2020

Apple, anticompetition, and censorship

On July 20, 2020, GreatFire wrote to all 13 members of the Subcommittee on Antitrust, Commercial and Administrative Law of the U.S. House Committee on the Judiciary, requesting a thorough examination into Apple’s practice of censorship of its App Store, and an investigation into how the company collaborates with the Chinese authorities to maintain its unique position as one of the few foreign tech companies operating profitably in the Chinese digital market.  

This letter was sent a week before Apple CEO TIm Cook will be called for questioning in front of the Subcommittee on Antitrust, Commercial and Administrative Law. The CEOs of Amazon, Google and Facebook will also be questioned on July 27, as part of the Committee’s ongoing investigation into competition in the digital marketplace.

This hearing offers an opportunity to detail to the Subcommittee how Apple uses its closed operating ecosystem to not only abuse its market position but also to deprive certain users, most notably those in China, of their right to download and use apps related to privacy, secure communication, and censorship circumvention.

We hope that U.S. House representatives agree with our view that Apple should not be allowed to do elsewhere what would be considered as unacceptable in the U.S. Chinese citizens are not second class citizens. Private companies such as Apple compromise themselves and their self-proclaimed values of freedom and privacy when they collaborate with the Chinese government and its censors.

星期一, 6月 10, 2019


苹果在涉及西藏的审查方面有着悠久历史。 2009年,据计算机世界网透露 ,与达赖喇嘛有关的几个应用程序在苹果的中国区应用商店中不存在。这些应用的开发者未收到他们的应用被删除的通知。当面对这些审查制度时,苹果发言人只是说该公司将“继续遵守当地法律”。

2017年12月,在中国的一次会议上,当被问及与中国当局合作审查苹果应用商店时,蒂姆·库克 宣称




“苹果的领导力隐藏在他们审查应用程序以遵守模糊的'中国当地法律'的借口,但他们的行为缺乏任何透明度。通过从中国苹果应用商店删除藏文和其他许多应用程序,苹果阻碍了藏人获取信息和自由表达自己的能力,这是国际法下的一项基本人权。“ TibCERT(西藏计算机应急准备小组)的响应协调员Dorjee Phuntsok说道。 他们与GreatFire合作对被屏蔽的应用程序进行了分析。

   2019年1月,GreatFire推出了。在那时,GreatFire联合创始人马丁约翰逊指出:“苹果公司在其透明度报告中没有分享有关应用商店审查的信息 - 该项目强制透明度。蒂姆库克可以随心所欲地说苹果在中国做了或没有做什么,但 提供了可以实际看到苹果实施审查原始数据的途径。




星期四, 6月 06, 2019


最新的 数字版权企业责任指数排名 就公司和政府需要做些什么来提出建议,以改善全球互联网用户的人权保护。数字版权排名(RDR)旨在通过为公司尊重和保护用户权利制定全球标准和激励措施,以促进互联网上的言论自由和隐私权。

在他们的2019年责任指数中,RDR着眼于24家世界上最重要的互联网公司在言论自由和隐私方面的政策,并强调了那些尚需努力和已经取得改进的公司。 RDR指出:


特别是,该报告强调了苹果如何滥用其网络言论的权力,并在中国指出这一点。根据该报告,苹果公司在面对政府当局提出的要求时,并未披露其从App Store中删除内容的数据。



RDR 建议政府要求公司的透明度并保持透明度。中国当局采取相反的做法 - 他们不希望在这些问题上保持透明度,因为它突显了他们不希望公众了解的信息。当局不希望公司透明,他们可能直接指示Apple不发布他们正删除的内容列表。

苹果可能真的认为他们必须遵守中国的法律条文。或者他们也可能愿意分享有关App Store中被审查内容的信息,但有碍于被中国当局束手束脚。苹果还可能会利用这种情况作为他们打击中国言论自由的掩护。无论Apple的真实动机如何,透明度都能够并已经被强加给他们。

在2019年1月,GreatFire发布了。该项目监控Apple在公司运营的每个市场中对App Store的审查。应用程序的可用性测试由网站访问者进行。截至今天,用户生成的测试已经确定了 超过1100个 在中国应用商店中不可用的应用。在中国受审查的应用程序包括那些涉及宗教,新闻,隐私和翻墙的应用程序。通过审查有助于规避审查限制的应用程序,苹果确实的让中国人无法自由访问信息。苹果的中国用户或许认为他们买到的是一流的设备 - 但可以肯定的是,该公司将他们视为二等信息公民。

RDR建议苹果对言论自由的限制保持透明,并公布有关公司因政府要求而删除内容所采取行动的数据。我们邀苹果审核我们在 上公开发布的数据,并根据中国当局的指示突出显示已删除应用的情况。

星期四, 11月 30, 2017


苹果对中国区的审查行为敞开了大门 - 但这似乎只是冰山一角。
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Intetesting point on xunlei. It lacks origin integrity checking (normally a big part of p2p). The problem is Xcode dpwnloads take ages as Apple does not provide it from a cdn within China. Maybe Apple themselves need to look at such a peer-to-peer accelerator.

Intetesting point on xunlei. It lacks origin integrity checking (normally a big part of p2p). The problem is Xcode dpwnloads take ages as Apple does not provide it from a cdn within China. Maybe Apple themselves need to look at such a peer-to-peer accelerator.

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