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iPhone FaceTime Vulnerability

This is kind of a crazy iPhone vulnerability: it’s possible to call someone on FaceTime and listen on their microphone — and see from their camera — before they accept the call.

This is definitely an embarrassment, and Apple was right to disable Group FaceTime until it’s fixed. But it’s hard to imagine how an adversary can operationalize this in any useful way.

New York governor Andrew M. Cuomo wrote: “The FaceTime bug is an egregious breach of privacy that puts New Yorkers at risk.” Kinda, I guess.

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Evaluating the GCHQ Exceptional Access Proposal

The so-called Crypto Wars have been going on for 25 years now. Basically, the FBI — and some of their peer agencies in the UK, Australia, and elsewhere — argue that the pervasive use of civilian encryption is hampering their ability to solve crimes and that they need the tech companies to make their systems susceptible to government eavesdropping. Sometimes their complaint is about communications systems, like voice or messaging apps. Sometimes it’s about end-user devices. On the other side of this debate is pretty much all technologists working in computer security and cryptography, who argue that adding eavesdropping features fundamentally makes those systems less secure.

A recent entry in this debate is a proposal by Ian Levy and Crispin Robinson, both from the UK’s GCHQ (the British signals-intelligence agency — basically, its NSA). It’s actually a positive contribution to the discourse around backdoors; most of the time government officials broadly demand that the tech companies figure out a way to meet their requirements, without providing any details. Levy and Robinson write:

In a world of encrypted services, a potential solution could be to go back a few decades. It’s relatively easy for a service provider to silently add a law enforcement participant to a group chat or call. The service provider usually controls the identity system and so really decides who’s who and which devices are involved — they’re usually involved in introducing the parties to a chat or call. You end up with everything still being end-to-end encrypted, but there’s an extra ‘end’ on this particular communication. This sort of solution seems to be no more intrusive than the virtual crocodile clips that our democratically elected representatives and judiciary authorise today in traditional voice intercept solutions and certainly doesn’t give any government power they shouldn’t have.

On the surface, this isn’t a big ask. It doesn’t affect the encryption that protects the communications. It only affects the authentication that assures people of whom they are talking to. But it’s no less dangerous a backdoor than any others that have been proposed: It exploits a security vulnerability rather than fixing it, and it opens all users of the system to exploitation of that same vulnerability by others.

In a blog post, cryptographer Matthew Green summarized the technical problems with this GCHQ proposal. Basically, making this backdoor work requires not only changing the cloud computers that oversee communications, but it also means changing the client program on everyone’s phone and computer. And that change makes all of those systems less secure. Levy and Robinson make a big deal of the fact that their backdoor would only be targeted against specific individuals and their communications, but it’s still a general backdoor that could be used against anybody.

The basic problem is that a backdoor is a technical capability — a vulnerability — that is available to anyone who knows about it and has access to it. Surrounding that vulnerability is a procedural system that tries to limit access to that capability. Computers, especially internet-connected computers, are inherently hackable, limiting the effectiveness of any procedures. The best defense is to not have the vulnerability at all.

That old physical eavesdropping system Levy and Robinson allude to also exploits a security vulnerability. Because telephone conversations were unencrypted as they passed through the physical wires of the phone system, the police were able to go to a switch in a phone company facility or a junction box on the street and manually attach alligator clips to a specific pair and listen in to what that phone transmitted and received. It was a vulnerability that anyone could exploit — not just the police — but was mitigated by the fact that the phone company was a monolithic monopoly, and physical access to the wires was either difficult (inside a phone company building) or obvious (on the street at a junction box).

The functional equivalent of physical eavesdropping for modern computer phone switches is a requirement of a 1994 U.S. law called CALEA — and similar laws in other countries. By law, telephone companies must engineer phone switches that the government can eavesdrop, mirroring that old physical system with computers. It is not the same thing, though. It doesn’t have those same physical limitations that make it more secure. It can be administered remotely. And it’s implemented by a computer, which makes it vulnerable to the same hacking that every other computer is vulnerable to.

This isn’t a theoretical problem; these systems have been subverted. The most public incident dates from 2004 in Greece. Vodafone Greece had phone switches with the eavesdropping feature mandated by CALEA. It was turned off by default in the Greek phone system, but the NSA managed to surreptitiously turn it on and use it to eavesdrop on the Greek prime minister and over 100 other high-ranking dignitaries.

There’s nothing distinct about a phone switch that makes it any different from other modern encrypted voice or chat systems; any remotely administered backdoor system will be just as vulnerable. Imagine a chat program added this GCHQ backdoor. It would have to add a feature that added additional parties to a chat from somewhere in the system — and not by the people at the endpoints. It would have to suppress any messages alerting users to another party being added to that chat. Since some chat programs, like iMessage and Signal, automatically send such messages, it would force those systems to lie to their users. Other systems would simply never implement the “tell me who is in this chat conversation” feature­which amounts to the same thing.

And once that’s in place, every government will try to hack it for its own purposes­ — just as the NSA hacked Vodafone Greece. Again, this is nothing new. In 2010, China successfully hacked the back-door mechanism Google put in place to meet law-enforcement requests. In 2015, someone — we don’t know who — hacked an NSA backdoor in a random-number generator used to create encryption keys, changing the parameters so they could also eavesdrop on the communications. There are certainly other stories that haven’t been made public.

Simply adding the feature erodes public trust. If you were a dissident in a totalitarian country trying to communicate securely, would you want to use a voice or messaging system that is known to have this sort of backdoor? Who would you bet on, especially when the cost of losing the bet might be imprisonment or worse: the company that runs the system, or your country’s government intelligence agency? If you were a senior government official, or the head of a large multinational corporation, or the security manager or a critical technician at a power plant, would you want to use this system?

Of course not.

Two years ago, there was a rumor of a WhatsApp backdoor. The details are complicated, and calling it a backdoor or a vulnerability is largely inaccurate — but the resultant confusion caused some people to abandon the encrypted messaging service.

Trust is fragile, and transparency is essential to trust. And while Levy and Robinson state that “any exceptional access solution should not fundamentally change the trust relationship between a service provider and its users,” this proposal does exactly that. Communications companies could no longer be honest about what their systems were doing, and we would have no reason to trust them if they tried.

In the end, all of these exceptional access mechanisms, whether they exploit existing vulnerabilities that should be closed or force vendors to open new ones, reduce the security of the underlying system. They reduce our reliance on security technologies we know how to do well — cryptography — to computer security technologies we are much less good at. Even worse, they replace technical security measures with organizational procedures. Whether it’s a database of master keys that could decrypt an iPhone or a communications switch that orchestrates who is securely chatting with whom, it is vulnerable to attack. And it will be attacked.

The foregoing discussion is a specific example of a broader discussion that we need to have, and it’s about the attack/defense balance. Which should we prioritize? Should we design our systems to be open to attack, in which case they can be exploited by law enforcement — and others? Or should we design our systems to be as secure as possible, which means they will be better protected from hackers, criminals, foreign governments and — unavoidably — law enforcement as well?

This discussion is larger than the FBI’s ability to solve crimes or the NSA’s ability to spy. We know that foreign intelligence services are targeting the communications of our elected officials, our power infrastructure, and our voting systems. Do we really want some foreign country penetrating our lawful-access backdoor in the same way the NSA penetrated Greece’s?

I have long maintained that we need to adopt a defense-dominant strategy: We should prioritize our need for security over our need for surveillance. This is especially true in the new world of physically capable computers. Yes, it will mean that law enforcement will have a harder time eavesdropping on communications and unlocking computing devices. But law enforcement has other forensic techniques to collect surveillance data in our highly networked world. We’d be much better off increasing law enforcement’s technical ability to investigate crimes in the modern digital world than we would be to weaken security for everyone. The ability to surreptitiously add ghost users to a conversation is a vulnerability, and it’s one that we would be better served by closing than exploiting.

This essay originally appeared on Lawfare.com.

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Security Vulnerabilities in Cell Phone Systems

Good essay on the inherent vulnerabilities in the cell phone standards and the market barriers to fixing them.

So far, industry and policymakers have largely dragged their feet when it comes to blocking cell-site simulators and SS7 attacks. Senator Ron Wyden, one of the few lawmakers vocal about this issue, sent a letter in August encouraging the Department of Justice to “be forthright with federal courts about the disruptive nature of cell-site simulators.” No response has ever been published.

The lack of action could be because it is a big task — there are hundreds of companies and international bodies involved in the cellular network. The other reason could be that intelligence and law enforcement agencies have a vested interest in exploiting these same vulnerabilities. But law enforcement has other effective tools that are unavailable to criminals and spies. For example, the police can work directly with phone companies, serving warrants and Title III wiretap orders. In the end, eliminating these vulnerabilities is just as valuable for law enforcement as it is for everyone else.

As it stands, there is no government agency that has the power, funding and mission to fix the problems. Large companies such as AT&T, Verizon, Google and Apple have not been public about their efforts, if any exist.

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Cell Phone Security and Heads of State

Earlier this week, the New York Times reported that the Russians and the Chinese were eavesdropping on President Donald Trump’s personal cell phone and using the information gleaned to better influence his behavior. This should surprise no one. Security experts have been talking about the potential security vulnerabilities in Trump’s cell phone use since he became president. And President Barack Obama bristled at — but acquiesced to — the security rules prohibiting him from using a “regular” cell phone throughout his presidency.

Three broader questions obviously emerge from the story. Who else is listening in on Trump’s cell phone calls? What about the cell phones of other world leaders and senior government officials? And — most personal of all — what about my cell phone calls?

There are two basic places to eavesdrop on pretty much any communications system: at the end points and during transmission. This means that a cell phone attacker can either compromise one of the two phones or eavesdrop on the cellular network. Both approaches have their benefits and drawbacks. The NSA seems to prefer bulk eavesdropping on the planet’s major communications links and then picking out individuals of interest. In 2016, WikiLeaks published a series of classified documents listing “target selectors”: phone numbers the NSA searches for and records. These included senior government officials of Germany — among them Chancellor Angela Merkel — France, Japan, and other countries.

Other countries don’t have the same worldwide reach that the NSA has, and must use other methods to intercept cell phone calls. We don’t know details of which countries do what, but we know a lot about the vulnerabilities. Insecurities in the phone network itself are so easily exploited that 60 Minutes eavesdropped on a US congressman’s phone live on camera in 2016. Back in 2005, unknown attackers targeted the cell phones of many Greek politicians by hacking the country’s phone network and turning on an already-installed eavesdropping capability. The NSA even implanted eavesdropping capabilities in networking equipment destined for the Syrian Telephone Company.

Alternatively, an attacker could intercept the radio signals between a cell phone and a tower. Encryption ranges from very weak to possibly strong, depending on which flavor the system uses. Don’t think the attacker has to put his eavesdropping antenna on the White House lawn; the Russian Embassy is close enough.

The other way to eavesdrop on a cell phone is by hacking the phone itself. This is the technique favored by countries with less sophisticated intelligence capabilities. In 2017, the public-interest forensics group Citizen Lab uncovered an extensive eavesdropping campaign against Mexican lawyers, journalists, and opposition politicians — presumably run by the government. Just last month, the same group found eavesdropping capabilities in products from the Israeli cyberweapons manufacturer NSO Group operating in Algeria, Bangladesh, Greece, India, Kazakhstan, Latvia, South Africa — 45 countries in all.

These attacks generally involve downloading malware onto a smartphone that then records calls, text messages, and other user activities, and forwards them to some central controller. Here, it matters which phone is being targeted. iPhones are harder to hack, which is reflected in the prices companies pay for new exploit capabilities. In 2016, the vulnerability broker Zerodium offered $1.5 million for an unknown iOS exploit and only $200K for a similar Android exploit. Earlier this year, a new Dubai start-up announced even higher prices. These vulnerabilities are resold to governments and cyberweapons manufacturers.

Some of the price difference is due to the ways the two operating systems are designed and used. Apple has much more control over the software on an iPhone than Google does on an Android phone. Also, Android phones are generally designed, built, and sold by third parties, which means they are much less likely to get timely security updates. This is changing. Google now has its own phone — Pixel — that gets security updates quickly and regularly, and Google is now trying to pressure Android-phone manufacturers to update their phones more regularly. (President Trump reportedly uses an iPhone.)

Another way to hack a cell phone is to install a backdoor during the design process. This is a real fear; earlier this year, US intelligence officials warned that phones made by the Chinese companies ZTE and Huawei might be compromised by that government, and the Pentagon ordered stores on military bases to stop selling them. This is why China’s recommendation that if Trump wanted security, he should use a Huawei phone, was an amusing bit of trolling.

Given the wealth of insecurities and the array of eavesdropping techniques, it’s safe to say that lots of countries are spying on the phones of both foreign officials and their own citizens. Many of these techniques are within the capabilities of criminal groups, terrorist organizations, and hackers. If I were guessing, I’d say that the major international powers like China and Russia are using the more passive interception techniques to spy on Trump, and that the smaller countries are too scared of getting caught to try to plant malware on his phone.

It’s safe to say that President Trump is not the only one being targeted; so are members of Congress, judges, and other senior officials — especially because no one is trying to tell any of them to stop using their cell phones (although cell phones still are not allowed on either the House or the Senate floor).

As for the rest of us, it depends on how interesting we are. It’s easy to imagine a criminal group eavesdropping on a CEO’s phone to gain an advantage in the stock market, or a country doing the same thing for an advantage in a trade negotiation. We’ve seen governments use these tools against dissidents, reporters, and other political enemies. The Chinese and Russian governments are already targeting the US power grid; it makes sense for them to target the phones of those in charge of that grid.

Unfortunately, there’s not much you can do to improve the security of your cell phone. Unlike computer networks, for which you can buy antivirus software, network firewalls, and the like, your phone is largely controlled by others. You’re at the mercy of the company that makes your phone, the company that provides your cellular service, and the communications protocols developed when none of this was a problem. If one of those companies doesn’t want to bother with security, you’re vulnerable.

This is why the current debate about phone privacy, with the FBI on one side wanting the ability to eavesdrop on communications and unlock devices, and users on the other side wanting secure devices, is so important. Yes, there are security benefits to the FBI being able to use this information to help solve crimes, but there are far greater benefits to the phones and networks being so secure that all the potential eavesdroppers — including the FBI — can’t access them. We can give law enforcement other forensics tools, but we must keep foreign governments, criminal groups, terrorists, and everyone else out of everyone’s phones. The president may be taking heat for his love of his insecure phone, but each of us is using just as insecure a phone. And for a surprising number of us, making those phones more private is a matter of national security.

This essay previously appeared in the Atlantic.

EDITED TO ADD: Steven Bellovin and Susan Landau have a good essay on the same topic, as does Wired. Slashdot post.

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Five-Eyes Intelligence Services Choose Surveillance Over Security

The Five Eyes — the intelligence consortium of the rich English-speaking countries (the US, Canada, the UK, Australia, and New Zealand) — have issued a “Statement of Principles on Access to Evidence and Encryption” where they claim their needs for surveillance outweigh everyone’s needs for security and privacy.

…the increasing use and sophistication of certain encryption designs present challenges for nations in combatting serious crimes and threats to national and global security. Many of the same means of encryption that are being used to protect personal, commercial and government information are also being used by criminals, including child sex offenders, terrorists and organized crime groups to frustrate investigations and avoid detection and prosecution.

Privacy laws must prevent arbitrary or unlawful interference, but privacy is not absolute. It is an established principle that appropriate government authorities should be able to seek access to otherwise private information when a court or independent authority has authorized such access based on established legal standards. The same principles have long permitted government authorities to search homes, vehicles, and personal effects with valid legal authority.

The increasing gap between the ability of law enforcement to lawfully access data and their ability to acquire and use the content of that data is a pressing international concern that requires urgent, sustained attention and informed discussion on the complexity of the issues and interests at stake. Otherwise, court decisions about legitimate access to data are increasingly rendered meaningless, threatening to undermine the systems of justice established in our democratic nations.

To put it bluntly, this is reckless and shortsighted. I’ve repeatedly written about why this can’t be done technically, and why trying results in insecurity. But there’s a greater principle at first: we need to decide, as nations and as society, to put defense first. We need a “defense dominant” strategy for securing the Internet and everything attached to it.

This is important. Our national security depends on the security of our technologies. Demanding that technology companies add backdoors to computers and communications systems puts us all at risk. We need to understand that these systems are too critical to our society and — now that they can affect the world in a direct physical manner — affect our lives and property as well.

This is what I just wrote, in Click Here to Kill Everybody:

There is simply no way to secure US networks while at the same time leaving foreign networks open to eavesdropping and attack. There’s no way to secure our phones and computers from criminals and terrorists without also securing the phones and computers of those criminals and terrorists. On the generalized worldwide network that is the Internet, anything we do to secure its hardware and software secures it everywhere in the world. And everything we do to keep it insecure similarly affects the entire world.

This leaves us with a choice: either we secure our stuff, and as a side effect also secure their stuff; or we keep their stuff vulnerable, and as a side effect keep our own stuff vulnerable. It’s actually not a hard choice. An analogy might bring this point home. Imagine that every house could be opened with a master key, and this was known to the criminals. Fixing those locks would also mean that criminals’ safe houses would be more secure, but it’s pretty clear that this downside would be worth the trade-off of protecting everyone’s house. With the Internet+ increasing the risks from insecurity dramatically, the choice is even more obvious. We must secure the information systems used by our elected officials, our critical infrastructure providers, and our businesses.

Yes, increasing our security will make it harder for us to eavesdrop, and attack, our enemies in cyberspace. (It won’t make it impossible for law enforcement to solve crimes; I’ll get to that later in this chapter.) Regardless, it’s worth it. If we are ever going to secure the Internet+, we need to prioritize defense over offense in all of its aspects. We’ve got more to lose through our Internet+ vulnerabilities than our adversaries do, and more to gain through Internet+ security. We need to recognize that the security benefits of a secure Internet+ greatly outweigh the security benefits of a vulnerable one.

We need to have this debate at the level of national security. Putting spy agencies in charge of this trade-off is wrong, and will result in bad decisions.

Cory Doctorow has a good reaction.

Slashdot post.

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Details on a New PGP Vulnerability

A new PGP vulnerability was announced today. Basically, the vulnerability makes use of the fact that modern e-mail programs allow for embedded HTML objects. Essentially, if an attacker can intercept and modify a message in transit, he can insert code that sends the plaintext in a URL to a remote website. Very clever.

The EFAIL attacks exploit vulnerabilities in the OpenPGP and S/MIME standards to reveal the plaintext of encrypted emails. In a nutshell, EFAIL abuses active content of HTML emails, for example externally loaded images or styles, to exfiltrate plaintext through requested URLs. To create these exfiltration channels, the attacker first needs access to the encrypted emails, for example, by eavesdropping on network traffic, compromising email accounts, email servers, backup systems or client computers. The emails could even have been collected years ago.

The attacker changes an encrypted email in a particular way and sends this changed encrypted email to the victim. The victim’s email client decrypts the email and loads any external content, thus exfiltrating the plaintext to the attacker.

A few initial comments:

1. Being able to intercept and modify e-mails in transit is the sort of thing the NSA can do, but is hard for the average hacker. That being said, there are circumstances where someone can modify e-mails. I don’t mean to minimize the seriousness of this attack, but that is a consideration.

2. The vulnerability isn’t with PGP or S/MIME itself, but in the way they interact with modern e-mail programs. You can see this in the two suggested short-term mitigations: “No decryption in the e-mail client,” and “disable HTML rendering.”

3. I’ve been getting some weird press calls from reporters wanting to know if this demonstrates that e-mail encryption is impossible. No, this just demonstrates that programmers are human and vulnerabilities are inevitable. PGP almost certainly has fewer bugs than your average piece of software, but it’s not bug free.

3. Why is anyone using encrypted e-mail anymore, anyway? Reliably and easily encrypting e-mail is an insurmountably hard problem for reasons having nothing to do with today’s announcement. If you need to communicate securely, use Signal. If having Signal on your phone will arouse suspicion, use WhatsApp.

I’ll post other commentaries and analyses as I find them.

EDITED TO ADD (5/14): News articles.

Slashdot thread.

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Oblivious DNS

Interesting idea:

…we present Oblivious DNS (ODNS), which is a new design of the DNS ecosystem that allows current DNS servers to remain unchanged and increases privacy for data in motion and at rest. In the ODNS system, both the client is modified with a local resolver, and there is a new authoritative name server for .odns. To prevent an eavesdropper from learning information, the DNS query must be encrypted; the client generates a request for www.foo.com, generates a session key k, encrypts the requested domain, and appends the TLD domain .odns, resulting in {www.foo.com}k.odns. The client forwards this, with the session key encrypted under the .odns authoritative server’s public key ({k}PK) in the “Additional Information” record of the DNS query to the recursive resolver, which then forwards it to the authoritative name server for .odns. The authoritative server decrypts the session key with his private key, and then subsequently decrypts the requested domain with the session key. The authoritative server then forwards the DNS request to the appropriate name server, acting as a recursive resolver. While the name servers see incoming DNS requests, they do not know which clients they are coming from; additionally, an eavesdropper cannot connect a client with her corresponding DNS queries.

News article.

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White House Chief of Staff John Kelly’s Cell Phone was Tapped

Politico reports that White House Chief of Staff John Kelly’s cell phone was compromised back in December.

I know this is news because of who he is, but I hope every major government official of any country assumes that their commercial off-the-shelf cell phone is compromised. Even allies spy on allies; remember the reports that the NSA tapped the cell phone of German Chancellor Angela Merkel?

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