March 15, 2021

by Bruce Schneier
Fellow and Lecturer, Harvard Kennedy School

A free monthly newsletter providing summaries, analyses, insights, and commentaries on security: computer and otherwise.

For back issues, or to subscribe, visit Crypto-Gram’s web page.

These same essays and news items appear in the Schneier on Security blog, along with a lively and intelligent comment section. An RSS feed is available.

In this issue:

  1. On Vulnerability-Adjacent Vulnerabilities
  2. Deliberately Playing Copyrighted Music to Avoid Being Live-Streamed
  3. US Cyber Command Valentine’s Day Cryptography Puzzles
  4. Malicious Barcode Scanner App
  5. Browser Tracking Using Favicons
  6. Virginia Data Privacy Law
  7. WEIS 2021 Call for Papers
  8. Router Security
  9. GPS Vulnerabilities
  10. Dependency Confusion: Another Supply-Chain Vulnerability
  11. Twelve-Year-Old Vulnerability Found in Windows Defender
  12. On Chinese-Owned Technology Platforms
  13. The Problem with Treating Data as a Commodity
  14. National Security Risks of Late-Stage Capitalism
  15. Mysterious Macintosh Malware
  16. Encoded Message in the Perseverance Mars Lander’s Parachute
  17. Chinese Hackers Stole an NSA Windows Exploit in 2014
  18. Four Microsoft Exchange Zero-Days Exploited by China
  19. Threat Model Humor
  20. No, RSA Is Not Broken
  21. Hacking Digitally Signed PDF Files
  22. On Not Fixing Old Vulnerabilities
  23. More on the Chinese Zero-Day Microsoft Exchange Hack
  24. Fast Random Bit Generation
  25. Metadata Left in Security Agency PDFs
  26. Upcoming Speaking Engagements

On Vulnerability-Adjacent Vulnerabilities

[2021.02.15] At the virtual Enigma Conference, Google’s Project Zero’s Maggie Stone gave a talk about zero-day exploits in the wild. In it, she talked about how often vendors fix vulnerabilities only to have the attackers tweak their exploits to work again. From a MIT Technology Review article:

Soon after they were spotted, the researchers saw one exploit being used in the wild. Microsoft issued a patch and fixed the flaw, sort of. In September 2019, another similar vulnerability was found being exploited by the same hacking group.

More discoveries in November 2019, January 2020, and April 2020 added up to at least five zero-day vulnerabilities being exploited from the same bug class in short order. Microsoft issued multiple security updates: some failed to actually fix the vulnerability being targeted, while others required only slight changes that required just a line or two to change in the hacker’s code to make the exploit work again.


“What we saw cuts across the industry: Incomplete patches are making it easier for attackers to exploit users with zero-days,” Stone said on Tuesday at the security conference Enigma. “We’re not requiring attackers to come up with all new bug classes, develop brand new exploitation, look at code that has never been researched before. We’re allowing the reuse of lots of different vulnerabilities that we previously knew about.”


Why aren’t they being fixed? Most of the security teams working at software companies have limited time and resources, she suggests — and if their priorities and incentives are flawed, they only check that they’ve fixed the very specific vulnerability in front of them instead of addressing the bigger problems at the root of many vulnerabilities.

Another article on the talk.

This is an important insight. It’s not enough to patch existing vulnerabilities. We need to make it harder for attackers to find new vulnerabilities to exploit. Closing entire families of vulnerabilities, rather than individual vulnerabilities one at a time, is a good way to do that.

Deliberately Playing Copyrighted Music to Avoid Being Live-Streamed

[2021.02.15] Vice is reporting on a new police hack: playing copyrighted music when being filmed by citizens, trying to provoke social media sites into taking the videos down and maybe even banning the filmers:

In a separate part of the video, which Devermont says was filmed later that same afternoon, Devermont approaches [BHPD Sgt. Billy] Fair outside. The interaction plays out almost exactly like it did in the department — when Devermont starts asking questions, Fair turns on the music.

Devermont backs away, and asks him to stop playing music. Fair says “I can’t hear you” — again, despite holding a phone that is blasting tunes.

Later, Fair starts berating Devermont’s livestreaming account, saying “I read the comments [on your account], they talk about how fake you are.” He then holds out his phone, which is still on full blast, and walks toward Devermont, saying “Listen to the music”.

In a statement emailed to VICE News, Beverly Hills PD said that “the playing of music while accepting a complaint or answering questions is not a procedure that has been recommended by Beverly Hills Police command staff,” and that the videos of Fair were “currently under review.”

However, this is not the first time that a Beverly Hills police officer has done this, nor is Fair the only one.

In an archived clip from a livestream shared privately to VICE Media that Devermont has not publicly reposted but he says was taken weeks ago, another officer can be seen quickly swiping through his phone as Devermont approaches. By the time Devermont is close enough to speak to him, the officer’s phone is already blasting “In My Life” by the Beatles — a group whose rightsholders have notoriously sued Apple numerous times. If you want to get someone in trouble for copyright infringement, the Beatles are quite possibly your best bet.

As Devermont asks about the music, the officer points the phone at him, asking, “Do you like it?”

Clever, really, and an illustration of the problem with context-free copyright enforcement.

US Cyber Command Valentine’s Day Cryptography Puzzles

[2021.02.15] The US Cyber Command has released a series of ten Valentine’s Day “Cryptography Challenge Puzzles.”

Slashdot thread. Reddit thread. (And here’s the archived link, in case Cyber Command takes the page down.)

Malicious Barcode Scanner App

[2021.02.16] Interesting story about a barcode scanner app that has been pushing malware on to Android phones. The app is called Barcode Scanner. It’s been around since 2017 and is owned by the Ukrainian company Lavabird Ldt. But a December 2020 update included some new features:

However, a rash of malicious activity was recently traced back to the app. Users began noticing something weird going on with their phones: their default browsers kept getting hijacked and redirected to random advertisements, seemingly out of nowhere.

Generally, when this sort of thing happens it’s because the app was recently sold. That’s not the case here.

It is frightening that with one update an app can turn malicious while going under the radar of Google Play Protect. It is baffling to me that an app developer with a popular app would turn it into malware. Was this the scheme all along, to have an app lie dormant, waiting to strike after it reaches popularity? I guess we will never know.

Browser Tracking Using Favicons

[2021.02.17] Interesting research on persistent web tracking using favicons. (For those who don’t know, favicons are those tiny icons that appear in browser tabs next to the page name.)

Abstract: The privacy threats of online tracking have garnered considerable attention in recent years from researchers and practitioners alike. This has resulted in users becoming more privacy-cautious and browser vendors gradually adopting countermeasures to mitigate certain forms of cookie-based and cookie-less tracking. Nonetheless, the complexity and feature-rich nature of modern browsers often lead to the deployment of seemingly innocuous functionality that can be readily abused by adversaries. In this paper we introduce a novel tracking mechanism that misuses a simple yet ubiquitous browser feature: favicons. In more detail, a website can track users across browsing sessions by storing a tracking identifier as a set of entries in the browser’s dedicated favicon cache, where each entry corresponds to a specific subdomain. In subsequent user visits the website can reconstruct the identifier by observing which favicons are requested by the browser while the user is automatically and rapidly redirected through a series of subdomains. More importantly, the caching of favicons in modern browsers exhibits several unique characteristics that render this tracking vector particularly powerful, as it is persistent (not affected by users clearing their browser data), non-destructive (reconstructing the identifier in subsequent visits does not alter the existing combination of cached entries), and even crosses the isolation of the incognito mode. We experimentally evaluate several aspects of our attack, and present a series of optimization techniques that render our attack practical. We find that combining our favicon-based tracking technique with immutable browser-fingerprinting attributes that do not change over time allows a website to reconstruct a 32-bit tracking identifier in 2 seconds. Furthermore,our attack works in all major browsers that use a favicon cache, including Chrome and Safari. Due to the severity of our attack we propose changes to browsers’ favicon caching behavior that can prevent this form of tracking, and have disclosed our findings to browser vendors who are currently exploring appropriate mitigation strategies.

Another researcher has implemented this proof of concept:

Strehle has set up a website that demonstrates how easy it is to track a user online using a favicon. He said it’s for research purposes, has released his source code online, and detailed a lengthy explanation of how supercookies work on his website.

The scariest part of the favicon vulnerability is how easily it bypasses traditional methods people use to keep themselves private online. According to Strehle, the supercookie bypasses the “private” mode of Chrome, Safari, Edge, and Firefox. Clearing your cache, surfing behind a VPN, or using an ad-blocker won’t stop a malicious favicon from tracking you.

EDITED TO ADD (3/12): There was an issue about whether this paper was inappropriately disclosed, and briefly deleted from the NDSS website. It was later put back with a prefatory note from the NDSS.

Virginia Data Privacy Law

[2021.02.18] Virginia is about to get a data privacy law, modeled on California’s law.

WEIS 2021 Call for Papers

[2021.02.18] The 20th Annual Workshop on the Economics of Information Security (WEIS 2021) will be held online in June. We just published the call for papers.

Router Security

[2021.02.19] This report is six months old, and I don’t know anything about the organization that produced it, but it has some alarming data about router security.

Conclusion: Our analysis showed that Linux is the most used OS running on more than 90% of the devices. However, many routers are powered by very old versions of Linux. Most devices are still powered with a 2.6 Linux kernel, which is no longer maintained for many years. This leads to a high number of critical and high severity CVEs affecting these devices.

Since Linux is the most used OS, exploit mitigation techniques could be enabled very easily. Anyhow, they are used quite rarely by most vendors except the NX feature.

A published private key provides no security at all. Nonetheless, all but one vendor spread several private keys in almost all firmware images.

Mirai used hard-coded login credentials to infect thousands of embedded devices in the last years. However, hard-coded credentials can be found in many of the devices and some of them are well known or at least easy crackable.

However, we can tell for sure that the vendors prioritize security differently. AVM does better job than the other vendors regarding most aspects. ASUS and Netgear do a better job in some aspects than D-Link, Linksys, TP-Link and Zyxel.

Additionally, our evaluation showed that large scale automated security analysis of embedded devices is possible today utilizing just open source software. To sum it up, our analysis shows that there is no router without flaws and there is no vendor who does a perfect job regarding all security aspects. Much more effort is needed to make home routers as secure as current desktop of server systems.

One comment on the report:

One-third ship with Linux kernel version 2.6.36 was released in October 2010. You can walk into a store today and buy a brand new router powered by software that’s almost 10 years out of date! This outdated version of the Linux kernel has 233 known security vulnerabilities registered in the Common Vulnerability and Exposures (CVE) database. The average router contains 26 critically-rated security vulnerabilities, according to the study.

We know the reasons for this. Most routers are designed offshore, by third parties, and then private labeled and sold by the vendors you’ve heard of. Engineering teams come together, design and build the router, and then disperse. There’s often no one around to write patches, and most of the time router firmware isn’t even patchable. The way to update your home router is to throw it away and buy a new one.

And this paper demonstrates that even the new ones aren’t likely to be secure.

GPS Vulnerabilities

[2021.02.22] Really good op-ed in the New York Times about how vulnerable the GPS system is to interference, spoofing, and jamming — and potential alternatives.

The 2018 National Defense Authorization Act included funding for the Departments of Defense, Homeland Security and Transportation to jointly conduct demonstrations of various alternatives to GPS, which were concluded last March. Eleven potential systems were tested, including eLoran, a low-frequency, high-power timing and navigation system transmitted from terrestrial towers at Coast Guard facilities throughout the United States.

“China, Russia, Iran, South Korea and Saudi Arabia all have eLoran systems because they don’t want to be as vulnerable as we are to disruptions of signals from space,” said Dana Goward, the president of the Resilient Navigation and Timing Foundation, a nonprofit that advocates for the implementation of an eLoran backup for GPS.

Also under consideration by federal authorities are timing systems delivered via fiber optic network and satellite systems in a lower orbit than GPS, which therefore have a stronger signal, making them harder to hack. A report on the technologies was submitted to Congress last week.

GPS is a piece of our critical infrastructure that is essential to a lot of the rest of our critical infrastructure. It needs to be more secure.

Dependency Confusion: Another Supply-Chain Vulnerability

[2021.02.23] Alex Birsan writes about being able to install malware into proprietary corporate software by naming the code files to be identical to internal corporate code files. From a ZDNet article:

Today, developers at small or large companies use package managers to download and import libraries that are then assembled together using build tools to create a final app.

This app can be offered to the company’s customers or can be used internally at the company as an employee tool.

But some of these apps can also contain proprietary or highly-sensitive code, depending on their nature. For these apps, companies will often use private libraries that they store inside a private (internal) package repository, hosted inside the company’s own network.

When apps are built, the company’s developers will mix these private libraries with public libraries downloaded from public package portals like npm, PyPI, NuGet, or others.


Researchers showed that if an attacker learns the names of private libraries used inside a company’s app-building process, they could register these names on public package repositories and upload public libraries that contain malicious code.

The “dependency confusion” attack takes place when developers build their apps inside enterprise environments, and their package manager prioritizes the (malicious) library hosted on the public repository instead of the internal library with the same name.

The research team said they put this discovery to the test by searching for situations where big tech firms accidentally leaked the names of various internal libraries and then registered those same libraries on package repositories like npm, RubyGems, and PyPI.

Using this method, researchers said they successfully loaded their (non-malicious) code inside apps used by 35 major tech firms, including the likes of Apple, Microsoft, PayPal, Shopify, Netflix, Yelp, Uber, and others.

Clever attack, and one that has netted him $130K in bug bounties.

More news articles.

Twelve-Year-Old Vulnerability Found in Windows Defender

[2021.02.24] Researchers found, and Microsoft has patched, a vulnerability in Windows Defender that has been around for twelve years. There is no evidence that anyone has used the vulnerability during that time.

The flaw, discovered by researchers at the security firm SentinelOne, showed up in a driver that Windows Defender — renamed Microsoft Defender last year — uses to delete the invasive files and infrastructure that malware can create. When the driver removes a malicious file, it replaces it with a new, benign one as a sort of placeholder during remediation. But the researchers discovered that the system doesn’t specifically verify that new file. As a result, an attacker could insert strategic system links that direct the driver to overwrite the wrong file or even run malicious code.

It isn’t unusual that vulnerabilities lie around for this long. They can’t be fixed until someone finds them, and people aren’t always looking.

On Chinese-Owned Technology Platforms

[2021.02.25] I am a co-author on a report published by the Hoover Institution: “Chinese Technology Platforms Operating in the United States.” From a blog post:

The report suggests a comprehensive framework for understanding and assessing the risks posed by Chinese technology platforms in the United States and developing tailored responses. It starts from the common view of the signatories — one reflected in numerous publicly available threat assessments — that China’s power is growing, that a large part of that power is in the digital sphere, and that China can and will wield that power in ways that adversely affect our national security. However, the specific threats and risks posed by different Chinese technologies vary, and effective policies must start with a targeted understanding of the nature of risks and an assessment of the impact US measures will have on national security and competitiveness. The goal of the paper is not to specifically quantify the risk of any particular technology, but rather to analyze the various threats, put them into context, and offer a framework for assessing proposed responses in ways that the signatories hope can aid those doing the risk analysis in individual cases.

The Problem with Treating Data as a Commodity

[2021.02.26] Excellent Brookings paper: “Why data ownership is the wrong approach to protecting privacy.”

From the introduction:

Treating data like it is property fails to recognize either the value that varieties of personal information serve or the abiding interest that individuals have in their personal information even if they choose to “sell” it. Data is not a commodity. It is information. Any system of information rights — whether patents, copyrights, and other intellectual property, or privacy rights — presents some tension with strong interest in the free flow of information that is reflected by the First Amendment. Our personal information is in demand precisely because it has value to others and to society across a myriad of uses.

From the conclusion:

Privacy legislation should empower individuals through more layered and meaningful transparency and individual rights to know, correct, and delete personal information in databases held by others. But relying entirely on individual control will not do enough to change a system that is failing individuals, and trying to reinforce control with a property interest is likely to fail society as well. Rather than trying to resolve whether personal information belongs to individuals or to the companies that collect it, a baseline federal privacy law should directly protect the abiding interest that individuals have in that information and also enable the social benefits that flow from sharing information.

National Security Risks of Late-Stage Capitalism

[2021.03.01] Early in 2020, cyberspace attackers apparently working for the Russian government compromised a piece of widely used network management software made by a company called SolarWinds. The hack gave the attackers access to the computer networks of some 18,000 of SolarWinds’s customers, including US government agencies such as the Homeland Security Department and State Department, American nuclear research labs, government contractors, IT companies and nongovernmental agencies around the world.

It was a huge attack, with major implications for US national security. The Senate Intelligence Committee is scheduled to hold a hearing on the breach on Tuesday. Who is at fault?

The US government deserves considerable blame, of course, for its inadequate cyberdefense. But to see the problem only as a technical shortcoming is to miss the bigger picture. The modern market economy, which aggressively rewards corporations for short-term profits and aggressive cost-cutting, is also part of the problem: Its incentive structure all but ensures that successful tech companies will end up selling insecure products and services.

Like all for-profit corporations, SolarWinds aims to increase shareholder value by minimizing costs and maximizing profit. The company is owned in large part by Silver Lake and Thoma Bravo, private-equity firms known for extreme cost-cutting.

SolarWinds certainly seems to have underspent on security. The company outsourced much of its software engineering to cheaper programmers overseas, even though that typically increases the risk of security vulnerabilities. For a while, in 2019, the update server’s password for SolarWinds’s network management software was reported to be “solarwinds123.” Russian hackers were able to breach SolarWinds’s own email system and lurk there for months. Chinese hackers appear to have exploited a separate vulnerability in the company’s products to break into US government computers. A cybersecurity adviser for the company said that he quit after his recommendations to strengthen security were ignored.

There is no good reason to underspend on security other than to save money — especially when your clients include government agencies around the world and when the technology experts that you pay to advise you are telling you to do more.

As the economics writer Matt Stoller has suggested, cybersecurity is a natural area for a technology company to cut costs because its customers won’t notice unless they are hacked — and if they are, they will have already paid for the product. In other words, the risk of a cyberattack can be transferred to the customers. Doesn’t this strategy jeopardize the possibility of long-term, repeat customers? Sure, there’s a danger there — but investors are so focused on short-term gains that they’re too often willing to take that risk.

The market loves to reward corporations for risk-taking when those risks are largely borne by other parties, like taxpayers. This is known as “privatizing profits and socializing losses.” Standard examples include companies that are deemed “too big to fail,” which means that society as a whole pays for their bad luck or poor business decisions. When national security is compromised by high-flying technology companies that fob off cybersecurity risks onto their customers, something similar is at work.

Similar misaligned incentives affect your everyday cybersecurity, too. Your smartphone is vulnerable to something called SIM-swap fraud because phone companies want to make it easy for you to frequently get a new phone — and they know that the cost of fraud is largely borne by customers. Data brokers and credit bureaus that collect, use, and sell your personal data don’t spend a lot of money securing it because it’s your problem if someone hacks them and steals it. Social media companies too easily let hate speech and misinformation flourish on their platforms because it’s expensive and complicated to remove it, and they don’t suffer the immediate costs — indeed, they tend to profit from user engagement regardless of its nature.

There are two problems to solve. The first is information asymmetry: buyers can’t adequately judge the security of software products or company practices. The second is a perverse incentive structure: the market encourages companies to make decisions in their private interest, even if that imperils the broader interests of society. Together these two problems result in companies that save money by taking on greater risk and then pass off that risk to the rest of us, as individuals and as a nation.

The only way to force companies to provide safety and security features for customers and users is with government intervention. Companies need to pay the true costs of their insecurities, through a combination of laws, regulations, and legal liability. Governments routinely legislate safety — pollution standards, automobile seat belts, lead-free gasoline, food service regulations. We need to do the same with cybersecurity: the federal government should set minimum security standards for software and software development.

In today’s underregulated markets, it’s just too easy for software companies like SolarWinds to save money by skimping on security and to hope for the best. That’s a rational decision in today’s free-market world, and the only way to change that is to change the economic incentives.

This essay previously appeared in the New York Times.

Mysterious Macintosh Malware

[2021.03.02] This is weird:

Once an hour, infected Macs check a control server to see if there are any new commands the malware should run or binaries to execute. So far, however, researchers have yet to observe delivery of any payload on any of the infected 30,000 machines, leaving the malware’s ultimate goal unknown. The lack of a final payload suggests that the malware may spring into action once an unknown condition is met.

Also curious, the malware comes with a mechanism to completely remove itself, a capability that’s typically reserved for high-stealth operations. So far, though, there are no signs the self-destruct feature has been used, raising the question of why the mechanism exists.

Besides those questions, the malware is notable for a version that runs natively on the M1 chip that Apple introduced in November, making it only the second known piece of macOS malware to do so. The malicious binary is more mysterious still because it uses the macOS Installer JavaScript API to execute commands. That makes it hard to analyze installation package contents or the way that package uses the JavaScript commands.

The malware has been found in 153 countries with detections concentrated in the US, UK, Canada, France, and Germany. Its use of Amazon Web Services and the Akamai content delivery network ensures the command infrastructure works reliably and also makes blocking the servers harder. Researchers from Red Canary, the security firm that discovered the malware, are calling the malware Silver Sparrow.

Feels government-designed, rather than criminal or hacker.

Another article. And the Red Canary analysis.

Encoded Message in the Perseverance Mars Lander’s Parachute

[2021.03.03] NASA made an oblique reference to a coded message in the color pattern of the Perseverance Mars Lander ‘s parachute.

More information.

Chinese Hackers Stole an NSA Windows Exploit in 2014

[2021.03.04] Check Point has evidence that (probably government affiliated) Chinese hackers stole and cloned an NSA Windows hacking tool years before (probably government affiliated) Russian hackers stole and then published the same tool. Here’s the timeline:

The timeline basically seems to be, according to Check Point:

  • 2013: NSA’s Equation Group developed a set of exploits including one called EpMe that elevates one’s privileges on a vulnerable Windows system to system-administrator level, granting full control. This allows someone with a foothold on a machine to commandeer the whole box.
  • 2014-2015: China’s hacking team code-named APT31, aka Zirconium, developed Jian by, one way or another, cloning EpMe.
  • Early 2017: The Equation Group’s tools were teased and then leaked online by a team calling itself the Shadow Brokers. Around that time, Microsoft cancelled its February Patch Tuesday, identified the vulnerability exploited by EpMe (CVE-2017-0005), and fixed it in a bumper March update. Interestingly enough, Lockheed Martin was credited as alerting Microsoft to the flaw, suggesting it was perhaps used against an American target.
  • Mid 2017: Microsoft quietly fixed the vulnerability exploited by the leaked EpMo exploit.

Lots of news articles about this.

Four Microsoft Exchange Zero-Days Exploited by China

[2021.03.04] Microsoft has issued an emergency Microsoft Exchange patch to fix four zero-day vulnerabilities currently being exploited by China.

EDITED TO ADD (3/12): Exchange Online is not affected.

Threat Model Humor

[2021.03.05] At a hospital.

No, RSA Is Not Broken

[2021.03.05] I have been seeing this paper by cryptographer Peter Schnorr making the rounds: “Fast Factoring Integers by SVP Algorithms.” It describes a new factoring method, and its abstract ends with the provocative sentence: “This destroys the RSA cryptosystem.”

It does not. At best, it’s an improvement in factoring — and I’m not sure it’s even that. The paper is a preprint: it hasn’t been peer reviewed. Be careful taking its claims at face value.

Some discussion here.

I’ll append more analysis links to this post when I find them.

EDITED TO ADD (3/12): The latest version of the paper does not have the words “This destroys the RSA cryptosystem” in the abstract. Some more discussion.

Hacking Digitally Signed PDF Files

[2021.03.08] Interesting paper: “Shadow Attacks: Hiding and Replacing Content in Signed PDFs“:

Abstract: Digitally signed PDFs are used in contracts and invoices to guarantee the authenticity and integrity of their content. A user opening a signed PDF expects to see a warning in case of any modification. In 2019, Mladenov et al. revealed various parsing vulnerabilities in PDF viewer implementations.They showed attacks that could modify PDF documents without invalidating the signature. As a consequence, affected vendors of PDF viewers implemented countermeasures preventing all attacks.

This paper introduces a novel class of attacks, which we call shadow attacks. The shadow attacks circumvent all existing countermeasures and break the integrity protection of digitally signed PDFs. Compared to previous attacks, the shadow attacks do not abuse implementation issues in a PDF viewer. In contrast, shadow attacks use the enormous flexibility provided by the PDF specification so that shadow documents remain standard-compliant. Since shadow attacks abuse only legitimate features,they are hard to mitigate.

Our results reveal that 16 (including Adobe Acrobat and Foxit Reader) of the 29 PDF viewers tested were vulnerable to shadow attacks. We introduce our tool PDF-Attacker which can automatically generate shadow attacks. In addition, we implemented PDF-Detector to prevent shadow documents from being signed or forensically detect exploits after being applied to signed PDFs.

EDITED TO ADD (3/12): This was written about last summer.

On Not Fixing Old Vulnerabilities

[2021.03.09] How is this even possible?

…26% of companies Positive Technologies tested were vulnerable to WannaCry, which was a threat years ago, and some even vulnerable to Heartbleed. “The most frequent vulnerabilities detected during automated assessment date back to 2013-2017, which indicates a lack of recent software updates,” the reported stated.

26%!? One in four networks?

Even if we assume that the report is self-serving to the company that wrote it, and that the statistic is not generally representative, this is still a disaster. The number should be 0%.

WannaCry was a 2017 cyberattack, based on a NSA-discovered and Russia-stolen-and-published Windows vulnerability. It primarily affects older, no-longer-supported products like Windows 7. If we can’t keep our systems secure from these vulnerabilities, how are we ever going to secure them from new threats?

More on the Chinese Zero-Day Microsoft Exchange Hack

[2021.03.10] Nick Weaver has an excellent post on the Microsoft Exchange hack:

The investigative journalist Brian Krebs has produced a handy timeline of events and a few things stand out from the chronology. The attacker was first detected by one group on Jan. 5 and another on Jan. 6, and Microsoft acknowledged the problem immediately. During this time the attacker appeared to be relatively subtle, exploiting particular targets (although we generally lack insight into who was targeted). Microsoft determined on Feb. 18 that it would patch these vulnerabilities on the March 9th “Patch Tuesday” release of fixes.

Somehow, the threat actor either knew that the exploits would soon become worthless or simply guessed that they would. So, in late February, the attacker changed strategy. Instead of simply exploiting targeted Exchange servers, the attackers stepped up their pace considerably by targeting tens of thousands of servers to install the web shell, an exploit that allows attackers to have remote access to a system. Microsoft then released the patch with very little warning on Mar. 2, at which point the attacker simply sought to compromise almost every vulnerable Exchange server on the Internet. The result? Virtually every vulnerable mail server received the web shell as a backdoor for further exploitation, making the patch effectively useless against the Chinese attackers; almost all of the vulnerable systems were exploited before they were patched.

This is a rational strategy for any actor who doesn’t care about consequences. When a zero-day is confidential and undiscovered, the attacker tries to be careful, only using it on attackers of sufficient value. But if the attacker knows or has reason to believe their vulnerabilities may be patched, they will increase the pace of exploits and, once a patch is released, there is no reason to not try to exploit everything possible.

We know that Microsoft shares advance information about updates with some organizations. I have long believed that they give the NSA a few weeks’ notice to do basically what the Chinese did: use the exploit widely, because you don’t have to worry about losing the capability.

Estimates on the number of affected networks continues to rise. At least 30,000 in the US, and 100,000 worldwide. More?

And the vulnerabilities:

The Chinese actors were not using a single vulnerability but actually a sequence of four “zero-day” exploits. The first allowed an unauthorized user to basically tell the server “let me in, I’m the server” by tricking the server into contacting itself. After the unauthorized user gained entry, the hacker could use the second vulnerability, which used a malformed voicemail that, when interpreted by the server, allowed them to execute arbitrary commands. Two further vulnerabilities allow the attacker to write new files, which is a common primitive that attackers use to increase their access: An attacker uses a vulnerability to write a file and then uses the arbitrary command execution vulnerability to execute that file.

Using this access, the attackers could read anybody’s email or indeed take over the mail server completely. Critically, they would almost always do more, introducing a “web shell,” a program that would enable further remote exploitation even if the vulnerabilities are patched.

The details of that web shell matter. If it was sophisticated, it implies that the Chinese hackers were planning on installing it from the beginning of the operation. If it’s kind of slapdash, it implies a last-minute addition when they realized their exploit window was closing.

Now comes the criminal attacks. Any unpatched network is still vulnerable, and we know from history that lots of networks will remain vulnerable for a long time. Expect the ransomware gangs to weaponize this attack within days.

EDITED TO ADD (3/12): Right on schedule, criminal hacker groups are exploiting the vulnerabilities.

EDITED TO ADD (3/13): And now the ransomware.

Fast Random Bit Generation

[2021.03.11] Science has a paper (and commentary) on generating 250 random terabits per second with a laser. I don’t know how cryptographically secure they are, but that can be cleaned up with something like Fortuna.

EDITED TO ADD (3/12): Here are free versions of the paper and the commentary.

Metadata Left in Security Agency PDFs

[2021.03.12] Really interesting research:

“Exploitation and Sanitization of Hidden Data in PDF Files”

Abstract: Organizations publish and share more and more electronic documents like PDF files. Unfortunately, most organizations are unaware that these documents can compromise sensitive information like authors names, details on the information system and architecture. All these information can be exploited easily by attackers to footprint and later attack an organization. In this paper, we analyze hidden data found in the PDF files published by an organization. We gathered a corpus of 39664 PDF files published by 75 security agencies from 47 countries. We have been able to measure the quality and quantity of information exposed in these PDF files. It can be effectively used to find weak links in an organization: employees who are running outdated software. We have also measured the adoption of PDF files sanitization by security agencies. We identified only 7 security agencies which sanitize few of their PDF files before publishing. Unfortunately, we were still able to find sensitive information within 65% of these sanitized PDF files. Some agencies are using weak sanitization techniques: it requires to remove all the hidden sensitive information from the file and not just to remove the data at the surface. Security agencies need to change their sanitization methods.

Short summary: no one is doing great.

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Bruce Schneier is an internationally renowned security technologist, called a security guru by the Economist. He is the author of over one dozen books — including his latest, We Have Root — as well as hundreds of articles, essays, and academic papers. His newsletter and blog are read by over 250,000 people. Schneier is a fellow at the Berkman Klein Center for Internet & Society at Harvard University; a Lecturer in Public Policy at the Harvard Kennedy School; a board member of the Electronic Frontier Foundation, AccessNow, and the Tor Project; and an Advisory Board Member of the Electronic Privacy Information Center and He is the Chief of Security Architecture at Inrupt, Inc.

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