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The Misaligned Incentives for Cloud Security

Russia’s Sunburst cyberespionage campaign, discovered late last year, impacted more than 100 large companies and US federal agencies, including the Treasury, Energy, Justice, and Homeland Security departments. A crucial part of the Russians’ success was their ability to move through these organizations by compromising cloud and local network identity systems to then access cloud accounts and pilfer emails and files.

Hackers said by the US government to have been working for the Kremlin targeted a widely used Microsoft cloud service that synchronizes user identities. The hackers stole security certificates to create their own identities, which allowed them to bypass safeguards such as multifactor authentication and gain access to Office 365 accounts, impacting thousands of users at the affected companies and government agencies.

It wasn’t the first time cloud services were the focus of a cyberattack, and it certainly won’t be the last. Cloud weaknesses were also critical in a 2019 breach at Capital One. There, an Amazon Web Services cloud vulnerability, compounded by Capital One’s own struggle to properly configure a complex cloud service, led to the disclosure of tens of millions of customer records, including credit card applications, Social Security numbers, and bank account information.

This trend of attacks on cloud services by criminals, hackers, and nation states is growing as cloud computing takes over worldwide as the default model for information technologies. Leaked data is bad enough, but disruption to the cloud, even an outage at a single provider, could quickly cost the global economy billions of dollars a day.

Cloud computing is an important source of risk both because it has quickly supplanted traditional IT and because it concentrates ownership of design choices at a very small number of companies. First, cloud is increasingly the default mode of computing for organizations, meaning ever more users and critical data from national intelligence and defense agencies ride on these technologies. Second, cloud computing services, especially those supplied by the world’s four largest providers — Amazon, Microsoft, Alibaba, and Google — concentrate key security and technology design choices inside a small number of organizations. The consequences of bad decisions or poorly made trade-offs can quickly scale to hundreds of millions of users.

The cloud is everywhere. Some cloud companies provide software as a service, support your Netflix habit, or carry your Slack chats. Others provide computing infrastructure like business databases and storage space. The largest cloud companies provide both.

The cloud can be deployed in several different ways, each of which shift the balance of responsibility for the security of this technology. But the cloud provider plays an important role in every case. Choices the provider makes in how these technologies are designed, built, and deployed influence the user’s security — yet the user has very little influence over them. Then, if Google or Amazon has a vulnerability in their servers — which you are unlikely to know about and have no control over — you suffer the consequences.

The problem is one of economics. On the surface, it might seem that competition between cloud companies gives them an incentive to invest in their users’ security. But several market failures get in the way of that ideal. First, security is largely an externality for these cloud companies, because the losses due to data breaches are largely borne by their users. As long as a cloud provider isn’t losing customers by the droves — which generally doesn’t happen after a security incident — it is incentivized to underinvest in security. Additionally, data shows that investors don’t punish the cloud service companies either: Stock price dips after a public security breach are both small and temporary.

Second, public information about cloud security generally doesn’t share the design trade-offs involved in building these cloud services or provide much transparency about the resulting risks. While cloud companies have to publicly disclose copious amounts of security design and operational information, it can be impossible for consumers to understand which threats the cloud services are taking into account, and how. This lack of understanding makes it hard to assess a cloud service’s overall security. As a result, customers and users aren’t able to differentiate between secure and insecure services, so they don’t base their buying and use decisions on it.

Third, cybersecurity is complex — and even more complex when the cloud is involved. For a customer like a company or government agency, the security dependencies of various cloud and on-premises network systems and services can be subtle and hard to map out. This means that users can’t adequately assess the security of cloud services or how they will interact with their own networks. This is a classic “lemons market” in economics, and the result is that cloud providers provide variable levels of security, as documented by Dan Geer, the chief information security officer for In-Q-Tel, and Wade Baker, a professor at Virginia Tech’s College of Business, when they looked at the prevalence of severe security findings at the top 10 largest cloud providers. Yet most consumers are none the wiser.

The result is a market failure where cloud service providers don’t compete to provide the best security for their customers and users at the lowest cost. Instead, cloud companies take the chance that they won’t get hacked, and past experience tells them they can weather the storm if they do. This kind of decision-making and priority-setting takes place at the executive level, of course, and doesn’t reflect the dedication and technical skill of product engineers and security specialists. The effect of this underinvestment is pernicious, however, by piling on risk that’s largely hidden from users. Widespread adoption of cloud computing carries that risk to an organization’s network, to its customers and users, and, in turn, to the wider internet.

This aggregation of cybersecurity risk creates a national security challenge. Policymakers can help address the challenge by setting clear expectations for the security of cloud services — and for making decisions and design trade-offs about that security transparent. The Biden administration, including newly nominated National Cyber Director Chris Inglis, should lead an interagency effort to work with cloud providers to review their threat models and evaluate the security architecture of their various offerings. This effort to require greater transparency from cloud providers and exert more scrutiny of their security engineering efforts should be accompanied by a push to modernize cybersecurity regulations for the cloud era.

The Federal Risk and Authorization Management Program (FedRAMP), which is the principal US government program for assessing the risk of cloud services and authorizing them for use by government agencies, would be a prime vehicle for these efforts. A recent executive order outlines several steps to make FedRAMP faster and more responsive. But the program is still focused largely on the security of individual services rather than the cloud vendors’ deeper architectural choices and threat models. Congressional action should reinforce and extend the executive order by adding new obligations for vendors to provide transparency about design trade-offs, threat models, and resulting risks. These changes could help transform FedRAMP into a more effective tool of security governance even as it becomes faster and more efficient.

Cloud providers have become important national infrastructure. Not since the heights of the mainframe era between the 1960s and early 1980s has the world witnessed computing systems of such complexity used by so many but designed and created by so few. The security of this infrastructure demands greater transparency and public accountability — if only to match the consequences of its failure.

This essay was written with Trey Herr, and previously appeared in Foreign Policy.

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Let’s Encrypt Vulnerability

The BBC is reporting a vulnerability in the Let’s Encrypt certificate service:

In a notification email to its clients, the organisation said: “We recently discovered a bug in the Let’s Encrypt certificate authority code.

“Unfortunately, this means we need to revoke the certificates that were affected by this bug, which includes one or more of your certificates. To avoid disruption, you’ll need to renew and replace your affected certificate(s) by Wednesday, March 4, 2020. We sincerely apologise for the issue.”

I am seeing nothing on the Let’s Encrypt website. And no other details anywhere. I’ll post more when I know more.

EDITED TO ADD: More from Ars Technica:

Let’s Encrypt uses Certificate Authority software called Boulder. Typically, a Web server that services many separate domain names and uses Let’s Encrypt to secure them receives a single LE certificate that covers all domain names used by the server rather than a separate cert for each individual domain.

The bug LE discovered is that, rather than checking each domain name separately for valid CAA records authorizing that domain to be renewed by that server, Boulder would check a single one of the domains on that server n times (where n is the number of LE-serviced domains on that server). Let’s Encrypt typically considers domain validation results good for 30 days from the time of validation–but CAA records specifically must be checked no more than eight hours prior to certificate issuance.

The upshot is that a 30-day window is presented in which certificates might be issued to a particular Web server by Let’s Encrypt despite the presence of CAA records in DNS that would prohibit that issuance.

Since Let’s Encrypt finds itself in the unenviable position of possibly having issued certificates that it should not have, it is revoking all current certificates that might not have had proper CAA record checking on Wednesday, March 4. Users whose certificates are scheduled to be revoked will need to manually force-renewal before then.

And Let’s Encrypt has a blog post about it.

EDITED TO ADD: Slashdot thread.

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Critical Windows Vulnerability Discovered by NSA

Yesterday’s Microsoft Windows patches included a fix for a critical vulnerability in the system’s crypto library.

A spoofing vulnerability exists in the way Windows CryptoAPI (Crypt32.dll) validates Elliptic Curve Cryptography (ECC) certificates.

An attacker could exploit the vulnerability by using a spoofed code-signing certificate to sign a malicious executable, making it appear the file was from a trusted, legitimate source. The user would have no way of knowing the file was malicious, because the digital signature would appear to be from a trusted provider.

A successful exploit could also allow the attacker to conduct man-in-the-middle attacks and decrypt confidential information on user connections to the affected software.

That’s really bad, and you should all patch your system right now, before you finish reading this blog post.

This is a zero-day vulnerability, meaning that it was not detected in the wild before the patch was released. It was discovered by security researchers. Interestingly, it was discovered by NSA security researchers, and the NSA security advisory gives a lot more information about it than the Microsoft advisory does.

Exploitation of the vulnerability allows attackers to defeat trusted network connections and deliver executable code while appearing as legitimately trusted entities. Examples where validation of trust may be impacted include:

  • HTTPS connections
  • Signed files and emails
  • Signed executable code launched as user-mode processes

The vulnerability places Windows endpoints at risk to a broad range of exploitation vectors. NSA assesses the vulnerability to be severe and that sophisticated cyber actors will understand the underlying flaw very quickly and, if exploited, would render the previously mentioned platforms as fundamentally vulnerable.The consequences of not patching the vulnerability are severe and widespread. Remote exploitation tools will likely be made quickly and widely available.Rapid adoption of the patch is the only known mitigation at this time and should be the primary focus for all network owners.

Early yesterday morning, NSA’s Cybersecurity Directorate head Anne Neuberger hosted a media call where she talked about the vulnerability and — to my shock — took questions from the attendees. According to her, the NSA discovered this vulnerability as part of its security research. (If it found it in some other nation’s cyberweapons stash — my personal favorite theory — she declined to say.) She did not answer when asked how long ago the NSA discovered the vulnerability. She said that this is not the first time the NSA sent Microsoft a vulnerability to fix, but it was the first time it has publicly taken credit for the discovery. The reason is that the NSA is trying to rebuild trust with the security community, and this disclosure is a result of its new initiative to share findings more quickly and more often.

Barring any other information, I would take the NSA at its word here. So, good for it.

And — seriously — patch your systems now: Windows 10 and Windows Server 2016/2019. Assume that this vulnerability has already been weaponized, probably by criminals and certainly by major governments. Even assume that the NSA is using this vulnerability — why wouldn’t it?

Ars Technica article. Wired article. CERT advisory.

EDITED TO ADD: Washington Post article.

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The NSA Warns of TLS Inspection

The NSA has released a security advisory warning of the dangers of TLS inspection:

Transport Layer Security Inspection (TLSI), also known as TLS break and inspect, is a security process that allows enterprises to decrypt traffic, inspect the decrypted content for threats, and then re-encrypt the traffic before it enters or leaves the network. Introducing this capability into an enterprise enhances visibility within boundary security products, but introduces new risks. These risks, while not inconsequential, do have mitigations.

[…]

The primary risk involved with TLSI’s embedded CA is the potential abuse of the CA to issue unauthorized certificates trusted by the TLS clients. Abuse of a trusted CA can allow an adversary to sign malicious code to bypass host IDS/IPSs or to deploy malicious services that impersonate legitimate enterprise services to the hosts.

[…]

A further risk of introducing TLSI is that an adversary can focus their exploitation efforts on a single device where potential traffic of interest is decrypted, rather than try to exploit each location where the data is stored.Setting a policy to enforce that traffic is decrypted and inspected only as authorized, and ensuring that decrypted traffic is contained in an out-of-band, isolated segment of the network prevents unauthorized access to the decrypted traffic.

[…]

To minimize the risks described above, breaking and inspecting TLS traffic should only be conducted once within the enterprise network. Redundant TLSI, wherein a client-server traffic flow is decrypted, inspected, and re-encrypted by one forward proxy and is then forwarded to a second forward proxy for more of the same,should not be performed.Inspecting multiple times can greatly complicate diagnosing network issues with TLS traffic. Also, multi-inspection further obscures certificates when trying to ascertain whether a server should be trusted. In this case, the “outermost” proxy makes the decisions on what server certificates or CAs should be trusted and is the only location where certificate pinning can be performed.Finally, a single TLSI implementation is sufficient for detecting encrypted traffic threats; additional TLSI will have access to the same traffic. If the first TLSI implementation detected a threat, killed the session, and dropped the traffic, then additional TLSI implementations would be rendered useless since they would not even receive the dropped traffic for further inspection. Redundant TLSI increases the risk surface, provides additional opportunities for adversaries to gain unauthorized access to decrypted traffic, and offers no additional benefits.

Nothing surprising or novel. No operational information about who might be implementing these attacks. No classified information revealed.

News article.

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NordVPN Breached

There was a successful attack against NordVPN:

Based on the command log, another of the leaked secret keys appeared to secure a private certificate authority that NordVPN used to issue digital certificates. Those certificates might be issued for other servers in NordVPN’s network or for a variety of other sensitive purposes. The name of the third certificate suggested it could also have been used for many different sensitive purposes, including securing the server that was compromised in the breach.

The revelations came as evidence surfaced suggesting that two rival VPN services, TorGuard and VikingVPN, also experienced breaches that leaked encryption keys. In a statement, TorGuard said a secret key for a transport layer security certificate for *.torguardvpnaccess.com was stolen. The theft happened in a 2017 server breach. The stolen data related to a squid proxy certificate.

TorGuard officials said on Twitter that the private key was not on the affected server and that attackers “could do nothing with those keys.” Monday’s statement went on to say TorGuard didn’t remove the compromised server until early 2018. TorGuard also said it learned of VPN breaches last May, “and in a related development we filed a legal complaint against NordVPN.”

The breach happened nineteen months ago, but the company is only just disclosing it to the public. We don’t know exactly what was stolen and how it affects VPN security. More details are needed.

VPNs are a shadowy world. We use them to protect our Internet traffic when we’re on a network we don’t trust, but we’re forced to trust the VPN instead. Recommendations are hard. NordVPN’s website says that the company is based in Panama. Do we have any reason to trust it at all?

I’m curious what VPNs others use, and why they should be believed to be trustworthy.

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New Reductor Nation-State Malware Compromises TLS

Kaspersky has a detailed blog post about a new piece of sophisticated malware that it’s calling Reductor. The malware is able to compromise TLS traffic by infecting the computer with hacked TLS engine substituted on the fly, “marking” infected TLS handshakes by compromising the underlining random-number generator, and adding new digital certificates. The result is that the attacker can identify, intercept, and decrypt TLS traffic from the infected computer.

The Kaspersky Attribution Engine shows strong code similarities between this family and the COMPfun Trojan. Moreover, further research showed that the original COMpfun Trojan most probably is used as a downloader in one of the distribution schemes. Based on these similarities, we’re quite sure the new malware was developed by the COMPfun authors.

The COMpfun malware was initially documented by G-DATA in 2014. Although G-DATA didn’t identify which actor was using this malware, Kaspersky tentatively linked it to the Turla APT, based on the victimology. Our telemetry indicates that the current campaign using Reductor started at the end of April 2019 and remained active at the time of writing (August 2019). We identified targets in Russia and Belarus.

[…]

Turla has in the past shown many innovative ways to accomplish its goals, such as using hijacked satellite infrastructure. This time, if we’re right that Turla is the actor behind this new wave of attacks, then with Reductor it has implemented a very interesting way to mark a host’s encrypted TLS traffic by patching the browser without parsing network packets. The victimology for this new campaign aligns with previous Turla interests.

We didn’t observe any MitM functionality in the analyzed malware samples. However, Reductor is able to install digital certificates and mark the targets’ TLS traffic. It uses infected installers for initial infection through HTTP downloads from warez websites. The fact the original files on these sites are not infected also points to evidence of subsequent traffic manipulation.

The attribution chain from Reductor to COMPfun to Turla is thin. Speculation is that the attacker behind all of this is Russia.

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CAs Reissue Over One Million Weak Certificates

Turns out that the software a bunch of CAs used to generate public-key certificates was flawed: they created random serial numbers with only 63 bits instead of the required 64. That may not seem like a big deal to the layman, but that one bit change means that the serial numbers only have half the required entropy. This really isn’t a security problem; the serial numbers are to protect against attacks that involve weak hash functions, and we don’t allow those weak hash functions anymore. Still, it’s a good thing that the CAs are reissuing the certificates. The point of a standard is that it’s to be followed.

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Detecting Phishing Sites with Machine Learning

Really interesting article:

A trained eye (or even a not-so-trained one) can discern when something phishy is going on with a domain or subdomain name. There are search tools, such as Censys.io, that allow humans to specifically search through the massive pile of certificate log entries for sites that spoof certain brands or functions common to identity-processing sites. But it’s not something humans can do in real time very well — which is where machine learning steps in.

StreamingPhish and the other tools apply a set of rules against the names within certificate log entries. In StreamingPhish’s case, these rules are the result of guided learning — a corpus of known good and bad domain names is processed and turned into a “classifier,” which (based on my anecdotal experience) can then fairly reliably identify potentially evil websites.

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E-Mailing Private HTTPS Keys

I don’t know what to make of this story:

The email was sent on Tuesday by the CEO of Trustico, a UK-based reseller of TLS certificates issued by the browser-trusted certificate authorities Comodo and, until recently, Symantec. It was sent to Jeremy Rowley, an executive vice president at DigiCert, a certificate authority that acquired Symantec’s certificate issuance business after Symantec was caught flouting binding industry rules, prompting Google to distrust Symantec certificates in its Chrome browser. In communications earlier this month, Trustico notified DigiCert that 50,000 Symantec-issued certificates Trustico had resold should be mass revoked because of security concerns.

When Rowley asked for proof the certificates were compromised, the Trustico CEO emailed the private keys of 23,000 certificates, according to an account posted to a Mozilla security policy forum. The report produced a collective gasp among many security practitioners who said it demonstrated a shockingly cavalier treatment of the digital certificates that form one of the most basic foundations of website security.

Generally speaking, private keys for TLS certificates should never be archived by resellers, and, even in the rare cases where such storage is permissible, they should be tightly safeguarded. A CEO being able to attach the keys for 23,000 certificates to an email raises troubling concerns that those types of best practices weren’t followed.

I am croggled by the multiple layers of insecurity here.

BoingBoing post.

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Signed Malware

Stuxnet famously used legitimate digital certificates to sign its malware. A research paper from last year found that the practice is much more common than previously thought.

Now, researchers have presented proof that digitally signed malware is much more common than previously believed. What’s more, it predated Stuxnet, with the first known instance occurring in 2003. The researchers said they found 189 malware samples bearing valid digital signatures that were created using compromised certificates issued by recognized certificate authorities and used to sign legitimate software. In total, 109 of those abused certificates remain valid. The researchers, who presented their findings Wednesday at the ACM Conference on Computer and Communications Security, found another 136 malware samples signed by legitimate CA-issued certificates, although the signatures were malformed.

The results are significant because digitally signed software is often able to bypass User Account Control and other Windows measures designed to prevent malicious code from being installed. Forged signatures also represent a significant breach of trust because certificates provide what’s supposed to be an unassailable assurance to end users that the software was developed by the company named in the certificate and hasn’t been modified by anyone else. The forgeries also allow malware to evade antivirus protections. Surprisingly, weaknesses in the majority of available AV programs prevented them from detecting known malware that was digitally signed even though the signatures weren’t valid.

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