Archive for July 2010
0 Comments | Posted by Enno Rey
… recently published here.
While I certainly agree with those comments stating that there’s a fishy element in the – conspiracy theory nurturing – story itself, this reminds me that Graeme Neilson (who gave the “Netscreen of the Dead” talk at Troopers, discussing modified firmware on Juniper and Fortinet devices) and I plan to give a talk on “Supply Chain (In-)Security” at this year’s Day-Con event. We still have to figure out with Angus if it fits into the agenda (and if we have enough material for an interesting 45 min storyline ;-)) though. Stay tuned for news on this here.
On a related note: for family reasons I won’t be able to make it to Vegas for Black Hat. Rene will take over my part in our talk “Burning Asgard – What happens when Loki breaks free” which covers some cool attacks on routing protocols and the release of an awesome tool Daniel wrote to implement those in a nice clicky-clicky way.
To all of you guys going to Vegas: have fun! and take care
0 Comments | Posted by Michael Thumann
According to SANS NewsBites Vol. XII, Issue 53 recently published there’s a lack of 3rd party developer support for some security features Microsoft introduced already years ago. We at ERNW have made similar observations when performing security assessments of COTS [commercial off-the-shelf] software. We therefore created a methodology, a proof of concept tool and a metric to test and to rate closed source software, where (amongst other approaches) these security features are checked and their (non-) presence contributes to an overall evaluation as for the trustworthiness of the applications in question. The concept “How to rate the security in closed source software” was presented to the public at Troopers10 and at Hack in the Box 2010 in Amsterdam. The slides can be found here.
Back on track as for one of our favorite rant subjects: desktop security. This stuff, commonly called the “LNK vulnerability”, has gained quite some momentum in the last days, including the release of a Metasploit module and a temporary raise of SANS Internet Storm Center‘s Infocon level to yellow (it’s back on green in the interim).
To give you a rough idea how this piece works, here’s a quote from the US-CERT advisory:
“Microsoft Windows fails to safely obtain icons for LNK files. When Windows displays Control Panel items, it will initialize each object for the purpose of providing dynamic icon functionality. This means that a Control Panel applet will execute code when the icon is displayed in Windows. Through use of an LNK file, an attacker can specify a malicious DLL that is to be processed within the context of the Windows Control Panel, which will result in arbitrary code execution. The specified code may reside on a USB drive, local or remote filesystem, a CD-ROM, or other locations. Viewing the location of a LNK file with Windows Explorer is sufficient to trigger the vulnerability.”
In short, as the Microsoft Malware Protection Center puts it: “[S]imply browsing to the removable media drive using an application that displays shortcut icons (like Windows Explorer) runs the malware without any additional user interaction.”
So actually, there is no exploitation in the sense of a buffer overflow of the LNK handling routines. The flaw just triggers downloading (and executing) some binary code. It’s basically about downloading some piece of code (to be executed on the local “compromised” box) from some location.
Figuring that brings us to an immediate discussion of potential mitigation strategies, which is – next to “some usual rant” – the main intent of this post.
As so often the US-CERT’s advisory provides good guidance on mitigating controls. It lists the following (most with a comment from my side):
a) Disable the displaying of icons for shortcuts.
Do not do this! It will most probably break your (users’) desktop experience in a horrible way.
Chester Wisniewski has a nice image of a treated desktop in yesterday’s post on the subject.
b) Disable AutoRun
This is pretty much always a good idea (security-wise), but it – partially – limits only one attack vector (removable media).
Interestingly enough the MS KB article on disabling Autorun functionality in Windows was last reviewed on 2010/07/01 and the CVE number for the LNK vulnerability was assigned 2010/06/30. There’s strange coincidences out there…
And, of course, not allowing untrusted USB devices to be connected to the organization’s machines usually is a good thing as well.
[for the record: yes, I know, there are organizations out where business tells you this is not possible for some reason or another. which might be true; I will not go into this debate right here and now. I just want to remind you, dear reader, of some good ole basics ;-)].
In the meantime people expect (and see) the vulnerability being exploited over network shares so focusing on removable media/USB devices alone might be too narrow-focused anyway.
c) Use least privilege
Aka: do not work as admin. I don’t really have to comment on this here, do I? It’s a no-brainer. Well, let’s say: it should be a no-brainer… when gathering with some infosec people from a >100K user environment recently I learned they still have about 30% of users with local admin privs…
[and don't get me wrong here: there might be good reasons for this. and those guys are not the only ones with such a landscape.]
To be discussed in more detail at another occasion.
d) Disable the WebClient service.
While I like this very much – given it’s a preventative control ["minimal machine approach"] and, btw, addresses other (past and potential future) vulnerabilities as well, e.g. those of MS10-045 published one week ago – it should be noted that this potentially breaks MS SharePoint (and other stuff as well).
So, unfortunately, again this will not be a feasible in quite some environments. Still, it might remind people that WebDAV is a technology that can be (ab-) used to access “network drives” in completely untrusted/untrustworthy locations.
e) Block outgoing SMB traffic
The (today) updated MS advisory provides another one:
f) Blocking the download of LNK and PIF files
Again, this is soo obvious that I refrain from any comment.
Those of you following this blog or our public statements on desktop security (like this one) regularly might have noticed that – as so often – the two main ones quite some organizations rely on are not mentioned here:
Patching: for the simple reason there’s no patch as of today (and the imp is out of the bottle, to public knowledge, five days now).
Antimalware “protections”: not sure how this could prevent downloading and executing arbitrary binary code. The announcements of major AV vendors “we now have a signature for this” mostly address the Stuxnet stuff found in the initial exploit, nothing else. So this is mostly window-dressing.
So far so good (or bad), the main point of this post is – and yes, I’m aware I needed a long warm-up today – the following: the security problem discussed here can be broken down to: “there’s a vulnerability that triggers an exploit that goes somewhere, downloads some code and executes it”.
Which, in turn, raises the fundamental question: why should some average corporate desktop computer be allowed to go to some arbitrary location, download code, and – above all – run this code.
Restricting where to get executable code from or, even better, just allowing a specified set of applications to run could (more or less) easily solve the kind of problems vulnerabilities like this one impose. And the technologies needed like – in MS space – Software Restriction Policies , Applocker or just (as part of SRPs) “path rules” restricting where to download executables from have been available for a long time.
As Marcus Ranum is much more eloquent than me – especially when it comes to ranting where he’s nearly unbeatable – I allow myself to quote him literally, from the “Schneier-Ranum Face-Off” on “Is antivirus dead?”:
“Of course, most organizations don’t know (or haven’t got the courage to discover) what programs they allow–and, ultimately, isn’t that the root of their security problems? When I read the security news and hear that thus-and-such government agency is trying to decide if Facebook is a necessary application, it makes my head spin. In Marcus-land, where I come from, you decide what is a necessary application first, not after you have 40,000 employees who have gotten so used to it that they now think Twitter is a constitutionally protected right. Isn’t a virus or malware just unauthorized execution that someone managed to sneak onto your machine? If we adopt a model whereby there are programs that are authorized (i.e., on a whitelist) and the operating system should terminate everything else, then malware and viruses are history, unless their authors can somehow fool the administrator into authorizing them to run.
Whenever I talk about execution control/whitelisting with corporate types, someone says, ‘But we don’t really have a way of determining all the applications that we use!’ Really? Wow. That sounds like a policy that’s basically, ‘We have no idea what our computers are for.’ In other words: ‘We’ve given up, and as far as we’re concerned, our computers are an unmanaged mess.’ Or to put it another way, malware heaven. Can anyone even calculate the cost of malware and viruses (as well as the occasional office time spent playing online games) to businesses? That cost, ultimately, is paid solely in order to avoid the difficulty of determining what programs are authorized — what’s the purpose of the computer an employee is provided to use?
Here’s why I keep talking about execution control: it’s actually ridiculously easy compared to dealing with antivirus and antimalware. So why isn’t everyone doing it? Because it’d dramatically cut down on our ability to goof off. If executives knew how easy it was to cut back on productivity-wasting goof-off-ware, don’t you think it would be happening all over the place by now? If, instead, we tell them it’s hard to know what executables we use in the office…well, what nobody knows won’t hurt anyone.”
Well said, Marcus. Nothing to add here.
So, please please please, just take a small amount (e.g. 1%) of the yearly budget you spend on antimalware software/support/operational cost, get a student intern in and have her start testing application whitelisting on some typical corporate desktops. This might contribute to a bit more sustainable security in your environment, one day in the future.
thanks for your time,
Interesting research from Stuart Schechter et.al. here.
They evaluated the effect that the removal or modification of online banking sites’ security features had on the users’ behavior (as for entering or withholding their passwords). Maybe for some of you not too surprising it turned out that the vast majority of users entered their passwords even if obviously alarming clues were present on the websites.
This, again, shows how important it is to understand how users behave, what their motives and incentives are and how to build environments that help them acting securely. This even more applies to corporate space. At times, bringing an industrial/organizational psychologist in might be a much better investment than writing yet-another-ignored-piece-of-policy.
have a great sunny sunday everybody,
Some days ago my old friend Pete Herzog from ISECOM posted a blog entry titled “Hackers May Be Giants with Sharp Teeth” here which – along with some quite insightful reflections on the way kids perceive “bad people” – contains his usual rant on (the uselessness of) risk assessment.
Given that this debate (whether taking a risk-based infosec approach is a wise thing or not) is a constant element of our – Pete’s and mine – long lasting relationship I somehow feel enticed to respond
Pete writes about a 9-yr-old girl who – when asked about “bad people” – stated that those “look like everybody else” and, referring to risk assessment, he concludes “that you can’t predict the threat realibly and therefore you can’t determine it.”
I fully agree here. I mean, if you _could_ predict the threat realibly why perform risk assessment at all? Taking decisions would simply be following a path of math then. Unfortunately most infosec practitioners do neither dispose of a crystal ball – at least not a dependable one – nor of the future prediction capabilities this entity seems to have …
So… as long as we can’t “determine reliably” we have to use … risk assessments. “Risk” deals with uncertainty. Otherwise it would be called “matter of fact”
Here’s how the “official vocabulary of risk management” (ISO Guide 73:2009) defines risk: “effect of uncertainty on objectives”.
Note that central term “uncertainty”? That’s what risk is about. And that’s, again, what risk assessments deal with. Deal with uncertainty. In situations where – despite that uncertainty – well-informed decisions have to be taken. Which is a quite common situation in an ISO’s professional life
Effective risk assessment helps answering questions in scenarios characterized by some degree of uncertainty. Questions like “In which areas do we have to improve in the next 12 months?” in (risk assessment) inventory mode or “Regarding some technology change in our organization, which are the main risks in this context and how do they change?” in governance mode. [See this presentation for an initial discussion of these terms/RA modes].
So asking for “reliable threat prediction/determination” from risk assessments is just not the right anticipation. In contrast, structured RA can certainly be regarded as the best way to “take the right decisions in complex environments and thereby get the optimal [increase of] security posture, while being limited by time/resource/political constraints and, at the same time, facing some uncertainty”.
Btw: the definition from ISO 73:2009 – that is used by recently published ISO 31000 (Risk management — Principles and guidelines) too – nicely shows the transformation the term “risk” has undergone in the last decade. From “risk = combination of probability and consequence of an event [threat]” in ISO 73:2002 through ISO 27005:2008’s inclusion of a “vulnerability element” (called “ease of exploitation” or “level of vulnerability” in the appendix) to the one in ISO 73:2009 cited above (which, for the first time, does not only focus on negative outcomes of events, but considers positive outcomes as well. which in turn reflects the concept of “risk & reward” increasingly used in some advanced/innovative infosec circles and to be discussed in this blog at another occasion).
Most (mature) approaches used amongst infosec professionals currently follow the “risk = likelihood * vulnerability * impact” line. We, at ERNW, use this one as well.
Which brings me to the next inaccuracy in Pete’s blog entry. He writes: “Threats are not the same for everyone nor do they actually effect us all the same. So why do we put up with risk assessments?”.
Indeed (most) threats _are_ the same for everyone. Malware is around, hardware fails from time to time and humans make errors. Point is all this does _not_ affect everyone “the same way” (those with the right controls will not get hit hardly by malware, those with server clusters will survive failing hardware more easily, those with evolved change control processes might have a better posture when it comes to consequences from human error). And all this is reflected by the – context-specific – “vulnerability factor” in risk assessments (and, for that matter, sometimes by the “impact factor” as well). So while threats might be the same, the _associated risks_ might/will not be the same.
which, again, is the exact reason for performing risk assessments ;-))
If they _were_ the same one just would have to look up some table distributed by $SOME_INDUSTRY_ASSOCIATION.
So, overall, I’m not sure that I can follow Pete’s line of arguments here. Maybe we should have a panel discussion on this at next year’s Troopers
have a good one everybody,
Yesterday we made our way to Vienna to participate and contribute to NinjaCon (formerly known as PlumberCon, before Nintendo Inc. claimed their rights ;)).
After our arrival Oliver held a five hour workshop on Penetration Testing and did the finishing touches on his slides about ‘Attacking Cisco Enterprise WLANs‘, which he will deliver later today together with Daniel. And last but not least Daniel will be the Packet Master of PacketWars™ Vienna taking place in the evening.
As sponsor of this young and vibrant conference we’re proud to share our equipment and know-how to support the networks on site.
Talking about young and vibrant: Last week we held one of our beloved internal workshops at ERNW to discuss the latest in ITSec and teamwork – but also to chat with colleagues or listen to a rant on $some-broken-technology of Enno. When having dinner on Tuesday we went crazy on planning for TROOPERS11. I don’t like it too much to talk about ‘good energy in the room’, but there was something really enthusiastic and insanely creative about it – and whatever it was, we gonna use it to make it even more enjoyable, educating and unforgettable than this year.
As we’re progressing at Vienna I’m going to update this blog post. So stay tuned!
Cheers, Florian & the team
UPDATE: NinjaCon is over. Besides the usual small hiccups at such an event it was a really great conference for all of us. Excellent speakers, an exciting location and the overall perfect atmosphere to interact, chat and learn really made the deal here. Big applause to the host @astera and her team!