How to Buy Precious Patching Time as Log4j Exploits Fly

Podcast: Cybereason shares details about its vaccine: a fast shot in the arm released within hours of the Apache Log4j zero-day horror show being disclosed.

Sure, Apache got a patch out fast when the Log4j logging library vulnerability – aka Javageddon or “up there with Shellshock” – exploded last week.

But emergency patches take days (best-case scenario) or weeks to install: plenty of time for attackers to do their worst.

Which they lickety-split did, and which they continue to do: Within hours of public disclosure of the flaw in the ubiquitous Java logging library, attackers were scanning for vulnerable servers and unleashing attacks to drop coin-miners, Cobalt Strike malware, the new Khonsari ransomware, the Orcus remote access trojan (RAT). reverse bash shells for future attacks, Mirai and other botnets, and backdoors. The list keeps growing.

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Time was, and is, of the essence. Fortunately, multiple security pros, including Marcus Hutchins and Cybereason researchers, saw a simple way to kneecap the dizzying array of exploits and whipped up a vaccine. On Friday, Cybereason released the open-source Logout4Shell: A quick shot in the arm that disables the problematic Java Naming and Directory Interface, or JNDI, at the heart of the Log4Shell zero-day exploit.

On Monday, after a hectic weekend, Cybereason CTO Yonatan Striem-Amit joined me on the Threatpost podcast to talk about Logout4Shell. It’s not a replacement for the patch, he emphasized. Rather, it’s a way for beleaguered organizations to buy themselves some time to patch at their leisure (or as close to “leisure” as you can get in such a situation).

Nor, mind you, is Logout4Shell a Hafnium-esque situation: Nobody’s installing a fix onto people’s servers without their permission, as the FBI did in April when it cleared ProxyLogon webshells from hundreds of organizations’ Microsoft Exchange servers without asking first.

“There’s something very compelling with the idea of white-hat hackers, applying these techniques globally and … becoming kind of a vigilante force for good,” Striem-Amit said. That’s the romantic stuff of Hollywood fairytale – at least, if you don’t have the National Security Agency (NSA) backing you up, as the FBI did with its Hafnium move. Rather, this is just about giving organizations an option to fix the problem fast.

You can download the podcast below, listen here or check out the lightly edited transcript that follows. For more podcasts, check out Threatpost’s podcast site.

Photo courtesy of SELF Magazine. Licensing details.

Lightly Edited Transcript

Lisa Vaas: Yonatan, thank you for joining us. Could you give us a look, first, before we jump into anything, about what kind of a crazy weekend you all must have had?

Yonatan Striem-Amit: We learned of the vulnerability on Friday morning, late, late night, Thursday night, and then had to, you know, start marching almost everybody in the company towards really three critical questions.

One was you know, are we ourselves vulnerable? We’re a software company. … Blessedly, after very deep verification, the answer was no. There was no crazy patching to do. But definitely it was an option, a possibility. The second question on our mind, of course, was are our customers vulnerable, and how can we help protect them?

And how can we as a security vendor help defend their customers? And the third one: How do we help the community? How can we help the community with something that was clear to become a huge issue? At the get-go, it was clear that it’s something that’s so trivial to exploit, so easy and so damaging and so prevalent, and it’s going to be very, very quickly weaponized.

Lisa Vaas: Well, yeah, just a string of code and that’s it. Well, I’m really glad you talked about how you as a company had to figure out if you were vulnerable, had to find out where that logging library might be. Cause I wanted to ask you about how amount of work it is for smaller businesses, for bigger businesses too, for this to suddenly get dropped into IT teams’ laps.

What does it mean for the average business, especially those without dedicated IT staff who were presumably on a frantic hunt for all the places that Log4J might reside in their environments? What does that scenario look like?

Yonatan Striem-Amit: Absolutely. This, this is one of the most prevalent libraries in the Java world right now, which is basically running about a third of the world’s servers, and each company had to look at their entire estate and ask themselves – looking from the most internet-facing with really everywhere – which of them are running Java?

If they’re running Java, are they using Log4J library in there? There’s not even a question of where they’re using it directly. The world of Java and open source has so many dependencies where a company might use one product, but it actually carries with it a dozen other libraries. So Log4J could be present even though a company might not necessarily even be aware or have had [installed] it directly.

So the scanning and the analysis is severely complex. And you have to go into each one of your servers and see, Are we using Log4J either directly or indirectly in that environment? And if the answer is yes, then how can we mitigate that risk? Which, again, is trivially exploitable to a single string and takes, you know, minutes to set up an exploitation .

So that was a very, very interesting weekend not just for us but for really every company out there, I would say.

Lisa Vaas: Are you hearing from people about how they’re getting their arms around it? Especially if they don’t have a dedicated security team? And how does it look if they use an MSP? Which applications should they be most worried about?

Yonatan Striem-Amit: Absolutely. So we’ve had kind of inbound traffic about people asking us about that exact same question and it boils down to, you have to have an understanding of what is your attack surface.

Generally, every server potentially could become a victim here because of the way self-replication has arisen. These days it allows for pretty complex interactions, but definitely companies should prioritize those servers [that] are internet-facing. And then one of the most prevalent attack scenarios we’ve seen [is] abusing things like the user agent or things like a logging screen.

It’s a very visual example. If an application has a logging page where a user is asked to put his username and password, and a lot of them do – it’s considered best practice that if a user’s failed to authenticate, you would write to the log saying “the user whose name is ABC and D just failed to authenticate.” But because of the severity of that vulnerability, an attacker could just supply the malicious string within that user field and get code execution on that server, [which] essentially controls logins, and therefore start doing whatever he wants on that server – including, of course, eavesdropping into every other user who’s logging in to the environment with their password.

So that’s the scope here. So when people are asking us, what should they prioritize, first and foremost, everything that’s internet-facing and then go down. At the end of the day, you really have to look at everything. Now, this becomes more complex, where a lot of companies are operating, on their premises and on the data center, applications and services that they don’t actually own the code for.

If you’re buying a software that’s deployed on-premise, you don’t necessarily have access into the innards of the server to start [unintelligible] or patching the Log4J libraries. So of course the supply chain questions here become more complex. And then when you add the MSP question that you asked earlier, it’s really about how do you make sure that you collaborate between the MSPs, the security team and the IT team or any company to really go and see, “Can we patch quickly enough? Can we go and install the mitigations that were published at the get-go over those servers? And if everything else fails, can we use Cybereason’s vaccine to help at least buy time in this scenario?”

Lisa Vaas: Let’s talk about the vaccine. Now, as I understand it, you guys pulled it off in about 20 minutes or something like that. You were looking at a workaround first flagged by Marcus Hutchins that disables indexing and then uses the vulnerability itself to apply it. Tell me about the timeline of when you first saw that workaround and put it into action.

Yonatan Striem-Amit: Absolutely. That’s actually a funny story. When the patch became available on the 9th in the morning, the Apache blog itself said that there was one mitigation that could be used, which is disabling the ability to do lookups.

That was the [Java Naming and Directory Interface, or JNDI] lookup capability. It’s at the heart of this threat. I was talking to my co-founder. It was probably around 10:00 AM or 11:00 AM at the time. And this was still when we were trying to make sure that both our sales and our customers are secure, so that was top of mind at this point.

And we’re talking about this vulnerability being so open. It’s so easy to use. We can actually create a payload that turns off and deploys that solution. He spent some time thinking about it. And one of our senior developers, Maayan Sela, and myself said, you know what? Let’s do it. Took probably about an hour and a half to get the vaccine initial release working.

And we’ve had at this point, an ability to set up an attack server, which, once you attack your own server environment, it basically shuts off and applies the … mitigation that was available at the time on that particular server, making the server effectively immune for that exploitation.

At that point, we said, you know, while this is a very, very nice thing to use, it’s such an important thing right now. We want to make it open source. So we’ve made a decision to go and release that to the public, put this code on, GitHub and try to push it as much as we can to make it available for others over the last … Marcus Hutchinson workaround, actually, I think.

Either later or about the same timelines, we [were] probably all of us looking at the same question at the same time, but the idea of weaponizing the vulnerability … exploiting it in order to vaccinate a server, really happened independently, given the information available by the Apache team themselves.

And later on, we discovered something interesting: that the mitigation was only working on versions that were pretty recent of LOg4J that still left an overwhelming overwhelmingly large number of servers globally that even that workaround could not work on. So he eventually ended up writing a new version of the vaccine that also fixes the vulnerability on versions that officially did not have the mitigation available for them, whose only option at the time was, really, go and patch your system [with the upgraded] version. Our vaccine now works across all versions of the library of Log4J. So definitely we’re hoping that has a positive impact.

Lisa Vaas: That is wild. I mean, not only did you spin on a dime to come up with this vaccine, but then you realized that it’s not going to take care of all versions, so you did it again. And you’re quality-testing this, and, well, kudos. I’m sure there are a lot of people who are very happy about it. I did want to ask you, I saw Check Point’s blog this morning about a slew of variations that are coming out, including takes on the initial exploit that can exploit the flaw, as they said, either over HTTP or HTTPS. Which, they said, could give attackers more alternatives to slip past new protections. I’m assuming that with the vaccine, it’s a done deal on these? Or are these new mutations of the initial exploit something we’re worried about, in spite of that vaccine, or what?

Yonatan Striem-Amit: Absolutely. So the industry’s overwhelming response across the threat has been, how do we add the detections to firewalls, to [Intrusion Prevents Services, or IPSes], to security devices? And we’re able to look at them, and most of [the exploit variations] were just looking for the string, the sequence of letters, JNDI … and the rest of it to detect this exploitation. However, very, very quickly it became clear that there are infinitely complex variations of this string, because of the way the Log4J library works. So any approach of trying to say, you know, block these sequences of letters from getting to a server, and that will be our solution, was bound, was bound for failure.

And all of those variations really failed on that same point that the flexibility that was built into the Log4J library allows attackers infinite ways of combining and creating that vulnerable sequence in a way that defenders and the network security companies could not define a solution for.

[That’s] kind of the heart of the challenge and the security industry. The vaccine works very, very differently. Once you infect a server, it completely shuts down the mechanism underlying that attack. No matter how much of a variation you use, as long as it uses the same vulnerability, and no matter what variation of the vulnerability is involved, they all get blocked because we basically remove the mechanism that does this, and the JNDI itself gets blocked, and therefore cannot be abused further cause it’s just removed from the server.

Lisa Vaas: Right. Well, great. So take that, attackers! You’re going to have to come up with another version. Another version of the Java [version of] Heartbleed or Shellshock. You’re going to have to start from scratch again. I was going to ask you how the vaccine differs from Apache’s official patch, but I think you’ve pretty much answered that. I mean, you’re disabling the support for custom format or look-ups. So you’re shutting down the mechanism that the exploit was working by.

Is there anything else you wanted to say about differentiation from Apache’s official patch, besides that people should absolutely install that patch as soon as possible?

Yonatan Striem-Amit: I think that’s the most critical thing. It’s still the patch. Do whatever you can to install the official pass as quickly as possible and make sure that you are as quickly as possible compliant with the latest version that they have.

But our purpose was, again, to buy time. And the biggest issue is, people were all around saying “My patch cycle is so complex. Installing this emergency patch right now is going to take me days, in the best case scenarios, and then weeks [in more complex scenarios]. Most likely, however, hackers wouldn’t give us that long to leisurely go and patch our system.”

They already have started with on the order of millions of scans across the internet, using that exploitation to attack servers. So our vaccine is there to help you buy time and kind of buy the peace of mind to go into the [proper] solution, “at your leisure quote, unquote.” Again, it’s not, actually leisurely – you absolutely should be using the official patch, but the vaccine is here to help you buy time to do it. And the period of time and the underlying mechanism is relatively similar.

The patch from Log4J basically disables the local mechanism and makes it a default configuration, unless people explicitly say we actually want to use that local mechanism. And what we do is very similar in the vaccine. We’re just doing it on a running system without restarting, without requiring, you know, the admins [to access] the shell account and then [have to redeploy] and everything.

Lisa Vaas: Yeah. It sounds pretty painless, which is nice with something of this magnitude. It doesn’t require a restart or reconfiguration of the server itself. So it’s super easy to do.

Yonatan Striem-Amit: Yep. That was our goal here to get something that’s as easy as possible to use. So you can buy yourself some time to fix the problem.

Lisa Vaas: Nicely done. Well, let me ask you: some assumed, I think maybe, that this [is some kind] of weaponizing of the actual vulnerability, [and it’s] brought images of what was done with Hafnium webshells on Exchange servers to mind. Somebody give me feedback on Cybereason’s vaccine and they said, well, you know, that means running the fix without permission on infrastructure, similar to what the FBI and [Department of Justice, or DOJ] did earlier this year to mitigate Hafnium.

Clarify for us why that’s wrong. This is not a weaponization that’s forced on anybody. Right?

Yonatan Striem-Amit: Yeah. So I think the premise of the question was absolutely accurate. I think there’s a huge difference between what we as a commercial company can do versus what the legal authorities, the FBI and the [National Security Agency, or NSA] can do in these cases.

We’re happy to provide the knowledge of technicalities, but we don’t have the [authority] to go and break into others’ network to fix them without their permission. This is something that needs to be a conscious decision done by the person, the person or people who own these servers, making a conscious decision that yes, they realize the criticality. They chose this as the right solution and they decided to deploy the solution on their environment, as well as monitor, you know, everything. That’s about the agency we expect for ourselves. What do we also accept from others? And we’re happy to make the [licensing] information available, you know, freely on GitHub.

But we cannot be the ones going in and hacking into other servers. Even if our intention is purely to help, this is something that people should do for themselves.

Lisa Vaas: Where do you think people got the idea that [the vaccine] was going to be inflicted on them?

Yonatan Striem-Amit: There’s something very compelling with the idea of white-hat hackers, applying these techniques globally and … becoming kind of a vigilante force for good.

But unfortunately that’s where the romanticism ends. We need to make sure that people can make a conscious decision where they understand the risk and the rewards. They understand their options. They understand what it means for them to vaccinate their servers and make a conscious decision to say, yes, this is what we want to do.

I believe we can provide the knowledge. We help our customers and we help anybody who says they have a problem right now, and we’re happy to assess, but it needs to be done by the person who owns the store.

Lisa Vaas: All right. Thank you for clarifying all of that. Any last thoughts for people who are scrambling to fix this?

Yonatan Striem-Amit: Yeah. Again, I think at the end of the day, really prioritize the most internet-facing environments, and rely on your service providers as much as they can to assist you with other patching. You’re welcome to use the vaccine to buy time. It does work remarkably well to make sure that you, between now and when you actually end up patching the server, you’re kind of secure.

So that’s a critical part of it. We’re here to help.

Lisa Vaas: Thank you so much. And thanks to everybody at Cybereason for coming up with this fix. I bet you made a lot of people’s lives a lot easier. So thank you for that.

Yonatan Striem-Amit: We do hope so. We’ve heard … feedback, very, very, very positive about how much this has been a help, and assistance in this time of great need. So then I can actually go … in a more controlled path cycle, more than with the scale of this vulnerability. That’s the best we can hope for.

Lisa Vaas: That’s great. Thank you so much for coming on. I really appreciate you taking the time with us.

Yonatan Striem-Amit: Thank you for hosting.

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  • Kristian on

    Super scary, we were so lucky that the software we use (apptec) wasn't affected by this since they don't use the Log4j library. We hope attackers weren't that successful in the end and the losses weren't to big for the affected companies.

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