This year at the SANS DFIR Summit in Austin, TX I had the distinct honor and pleasure of presenting a talk entitled To Silo, or Not to Silo: That is the Question. The PDF of the slides is available here (direct download). All the other awesome presentations are up there as well, so make time to check them out if you haven't already.
Shortly after the Summit, I promised someone somewhere (or told, or maybe just suggested) that I would post the notes, or at least more details, about the talk. After all, we all know how entertaining it is to look at the slides of a presentation. Wow, great stuff, right? I think there are supposed to be videos of the talks somewhere or other, but if there was a post about it, I missed it, and mine might not've been taped anyway, and well, who knows. So basically, the point of this is to flesh out that presentation in a meaningful way for those who are readers of the word rather than hearers (and obviously, not everyone could - or even want to - be there). That said, my intent here is not to recreate the presentation (although I might steal a slide or two), but rather to build on it, and present the topic in a slightly (well, maybe more than slightly) different format. As an aside, you might be wondering what took me so long to get this done. Well, just like a nice single-malt scotch, some things must age to perfection, and not leave the cask for bottling until they're just right.
A little background first, to help set the stage, and fair warning - this may be a bit long, and I may break it up into multiple posts (or I may not). Also, this is a blog post, not a white paper or news article, so it will be more "conversational" in nature. Hopefully, you will find it worth your while to soldier on through it. The genesis for the talk actually came from last year's Summit, with Alex Bond's lightning talk about combining host and network indicators. This made a lot of sense to me, and I thought it could be a full talk; plus, it falls in line with what I spend a lot of my time doing for a living.
Starting off, my focus was on the need to broaden our horizons from an evidence perspective; if we only look at host images, or RAM, or firewall logs, or netflow, or (the list goes on...), and we don't consider other sources, we're selling ourselves short. There are a couple difficulties with this type of approach, I think it bears calling them out now:
1. Not all evidence types are always available. This could be because they don't exist, or because you're not provided access to them.
2. Not all analysts/investigators/whatever you want to call them have in-depth knowledge, skills, and abilities with all evidence types.
Both those things are limiting factors, and so I started building from the standpoints of:
1. Dealing with the evidence you have, and expanding where you can.
2. Know how to deal with the evidence types available to you, and how to expand those.
3. If you can't/don't/won't then you're selling yourself and your client (internal or external) short.
To me, these things all related to siloing oneself, and so I came up with the title I did, way back last year (had to have the title before I could submit the talk in the first place). I mention that mainly because Jack Crook has a great blog post very similarly named, and touching on some of the same concepts, from May of this year. Read it, it's good, as is the norm for his blog. Just know that these were both conceived independent of one another; it must be a "great minds think alike" sort of thing, if I may in any way lay claim to that adage.
However, as I delved more into the topic at hand, I added another piece, which I feel it all really boils down to, and which if we ignore, can REALLY be siloing ourselves. It's one that business people can relate to (which is very important for us in our line of work), and which really guides our decision-making processes in Information Security as a whole. You haven't guessed yet? Well, it's risk. That's right - risk. Virtually all of the decisions we make in the course of DFIR work are based on, or informed by, risk. The "problem" is, we don't tend to see it that way, and that's odd to me, because in InfoSec we talk about it all the time (it's how we relate "bad things" to the business, get money for projects, tell people no, tell people yes, get hated/loved/ice water dumped on, so on and so forth). To be honest, I'm guilty of that as well - I could easily quantify various "needs" in that respect, but it really wasn't until I started working on the presentation, that I started seeing the correlation to the topic of risk.
Is risk really such an odd topic for us? I honestly don't think so, it's just we don't think of it in those terms. We'll take something really simple - would you close your eyes and attempt to walk across a busy intersection? Most likely not, but why? Because it's "stupid" or "idiotic" or a "good way to get killed"? Doesn't it really boil down to a risk decision, though? The risk of getting mowed down by a speeding motorist in a 2000-lb vehicle is greater than the reward of saying you crossed the intersection with your eyes closed. It's not that it's "stupid," it's just too risky for most people.
All the Things
So let's start to put it in the context of DFIR, and the scope of my Summit talk. In the presentation, I started off with a slide showing some different broad sources of evidence: Systems, Network, Cloud, Mobile; with the "Internet of Things" we may need to start adding in things like Appliances and Locks as well. Anyway, within those broad categories or families, there are subsets of types of evidence, such as:
Now, obviously there are many more than that, and some (such as Reverse Engineering/RE) aren't exactly evidence per se - but the idea was to start to get the audience thinking about the things they do during a given investigation (which may vary considerably, depending on the type, scope, and sensitivity of the matter at hand). I'm pretty sure that there are folks who don't regularly touch all, or even most, of just these few. With that in mind, do you know these and more in great detail? If you were handed one at random, would you know what to do with it? Would it make you uncomfortable? What if you were asked where to find it during an investigation? You don't have to answer out loud - again, the point is get us all thinking. If you think of each of these (or other) types/sources/etc of evidence as languages, wouldn't you want to be fluent? Don't you think it would be valuable? That's the first point.
In the preso, I illustrated this point - that of Knowledge, Skills, and Abilities (KSAs) - by taking everyone back to their days of role-playing games (I realize for some this might still be reality). Not modern MMORPGs, but old-school things like A/D&D, with character sheets, a bag full of dice, a DM (Dungeon Master, not direct message) and a bunch of chips and salsa. Yes, I know, for some there were probably "other" substances involved, but this is a family show, okay? Anyway, back in those simpler times, I always wanted to be more than just one character class during an adventure, especially if there were only a handful in the game (kind of like most DFIR teams); with only one of a few types, if someone got hurt, killed, or otherwise taken out of action, it was a disaster (in InfoSec terms, a single point of failure). I mean, if your thief got caught and killed while picking a pocket, who was there to open locks or detect traps for group? But, if you had a fighter/thief as well, then you have at least somewhat of a backup plan (again in InfoSec terms, a Disaster Recovery and Business Continuity/DRBC plan, and not just a single point of failure). So it's one thing to know one thing very well, but brings more value and broadens the overall potential of the group (or DFIR team) if you have folks with a broader skill set, such as a dual-class human or multi-class non-human. In this context, we're talking about people who can take apart a packet capture, reverse-engineer a binary, parse a memory dump, and so forth - they're not stuck with just one thing. This was the point that Jack raised in his blog post, and he draws it out very well.
Shelly Giesbrecht did a presentation at the Summit this year about building an awesome SOC, available here (direct PDF download). In a SOC, it's pretty common to have each member focused on a single monitoring task - firewall, IDS/IPS, DLP, AV, etc, and while that can provide a level of expertise in that area like Elminster does magic, it doesn't produce a very well-rounded individual (can the AV person fill in for the pcap?). As Shelly mentioned in her talk, the counter to that is to try to expand the knowledge base, but at the expense of actual abilities - we become jacks of all trades, but masters of none. This goes directly counter to what the greatest swordsman in all of history (no, not Yoda - Miyamoto Musashi) wrote in his Book of Five Rings - that in order to truly be a master of one thing (such as swordsmanship), you had to become a master of all things (poetry, tea ceremony, carpentry, penmanship). Troy Larson, in his keynote address at the Summit, (direct PDF download) brought up the concept of using the whole pig. And if you don't know about the whole pig, you can't use the whole pig, which is this point. But, if you don't have the whole pig, or don't look at parts of the pig, then you're missing out. And that's the second point.
A Puzzling Equation
Alex's lightning talk brought up the topic of using multiple sources of evidence - specifically host-based and network-based data - to better understand an attack. Yes, that's right - he was using more than one part of the pig (Troy would be proud, I'm sure). But as we saw earlier, there are more sources than just host/systems and network, and a multitude of evidence types within those, and that's where it starts to get a little more complicated, at least for some (and in some cases). The reason I say that is that I know people who for whatever reason, during an investigation focus on a single type of evidence or analysis, even when they have the skills to expand on it. For instance, they may just look at network logs, or a disk image, or volatile data. Each of these things can bring incredible value to an investigation, but individually, they're limited; if you don't expand your viewpoint, you're missing the bigger picture. I'll flesh that out with a puzzle illustration. We've probably all put together at least one puzzle in our lifetime, and even if it's not a normal occurrence for us, we understand the basic concepts (if not, wikiHow lays them out in a very simple format here).
Imagine you've been handed a pile of puzzle pieces, perhaps it looks something like this:
In other words, you have no idea how many pieces there are (or are supposed to be), nor what it should show when it's all put together. In case it's not perfectly clear, this puzzle is the investigation (whether it's internal/corporate, external/consulting, law enforcement, military, digital forensics, or incident response). The end goal is being able to deliver a concise, detailed report of findings that will properly inform the necessary parties of the facts (and in some cases, opinions) of what happened in a given scenario. If we take a bunch of the pieces out and put them in another box somewhere, not using them, that's probably not going to help us put it all together (so if you ignore RAM, or disk, or network...). If we follow the wikiHow article and start framing in the puzzle, then start taking guesses as to what it represents (or what happened during the commission of a crime, etc), then we're missing the bigger picture. Get it? Picture? The puzzle makes a picture - see what I did there? Heh heh heh. ;-)
I mean, this probably includes sea life, but we don't know for sure what is represented, and certainly can't answer any detailed questions about it...
What if we start to fill more pieces in? When can we start to (or best) answer questions? Here:
Pretty clearly the last one gives us the best chance of answering the most questions, but we could still miss some critical ones, because there are substantial blank areas. Sure, it appears to be foliage that's displayed in the background, but is it the real thing, or a reflection off the water? Is it made up of trees, bushes, or a combination? Is there any additional wildlife? What about predators? Imagine you're sitting down across from a group of attorneys (maybe friendly, maybe not), and those gaps are due to evidence not analyzed in the course of your investigation? Ouch...
Now, there are multiple facets to every investigation, and within each as well. There are differences between eDiscovery (loosely connected to what we do), digital forensics, and incident response, and those can probably all be argued to the nth degree and until the cows come home. I get all that, and am taking those things into account; I'm trying to paint a broader picture here, and get everyone to think about associated risk. In the end, it really is about risk, and I'll get to that. For now, let's list out a few scenarios that challenge the "all the pieces" approach.
- There isn't enough time to gather all available evidence types. This is probably most prevalent for IR cases, where time is of the essence, and imaging 500 systems that all have 500GB hard drives when you only have two people working on it, and executives/legal/PR/law enforcement need answers - fast.
- There aren't enough resources to gather all available evidence types. Again, very common in IR cases, where you have small teams, responsibilities are divided up, and KSAs may be lacking. We talked about that before.
- All evidence is not made available to you. This factors in across the board, and comes into play in pretty much every investigative role (corporate, consulting, LE, etc). This could be because:
- The business/client/suspect is trying to hide things from you.
- The people/groups in charge of the evidence are resistant/can't be bothered/etc (I've had CIOs refuse to give me access to systems because it was "too sensitive" and we ended up not gathering certain potential evidence).
- The evidence simply doesn't exist (systems/platforms don't exist, policies purge logs w/o central storage, power was shut down, it was intentionally destroyed, etc).
This is where we get to that part that didn't really dawn on me until I was well into building the presentation. Initially, the presentation was going to walk the audience through various investigative scenarios, to show how it was important to know how to handle different types and sources of evidence, and how without doing so, you could be missing the bigger picture (or the finer details within the picture, such as Mari DeGrazia's talk on Google Analytics cookies - direct PDFdownload. I still accomplished that, but also added in the new element, that of risk.
I can see it in your eyes, some of you are confused about what this has to do with risk. Wikipedia explains risk in part as "...the potential of losing something of value, weighed against the potential to gain something of value." It's a very familiar concept in financial circles, especially with regard to the return on investment (ROI) of a particular financial transaction. As such, it's very commonplace in businesses (especially mature ones), along with executives and business leaders. Information Security uses risk management as a means (among other things) to help quantify and show value to the business, especially preemptively or proactively, to help avoid increased costs from a negative occurrence (such as a breach) down the road. Businesses understand that, because they can recognize the cost associated with a breach, with damage to brand, lawsuits, expenses to clean up, and so forth. Okay, great, that makes perfect sense - but how does it apply to an after-the-fact situation in DFIR? Well, remember our two main points to which the risk pertains? Lack of knowledge, Lack of Evidence. I'll give some examples under each, for how risk ties in (please be warned - these won't be exhaustive).
Lack of knowledge/skills/abilities - personnel lacking a broad base of expertise in dealing with multiple times of evidence or investigations spanning computers, networks, cloud-based offerings, mobile technologies, etc.
- Requires additional/new internal or external (consulting) staffing resources, which cost money.
- Takes longer to complete investigations, which costs additional money, directly and indirectly (fines and fees, for instance).
- May result in inaccurate findings/reports/testimony, and could result in sanctions, fees, fines, settlements, etc.
- Loss of personnel who seek other positions to get the training/experience they know they need.
- Inability to spot incidents in the first place, leading to additional exposure and associated costs.
- Training staff to achieve higher levels of expertise in new areas costs money.
These are pretty straight-forward, no-brainer sort of things, right? I think we can all see the importance of being a well-rounded investigator; it makes us more valuable to our employer, and helps us do our jobs more effectively. Win-win scenario.
Lack of evidence - whether evidence is missing/doesn't exist, inaccessible or not provided, or simply overlooked/ignored.
- Inability to answer questions for which the answers can only be found in the "missing" evidence; can result in additional costs:
- Having to go back after the fact and attempt to recover other evidence types (paying more consultants, for example).
- Potential sanctions, fines, fees due to failure in fiduciary duties, legal responsibilities, and regulatory requirements.
- Loss of personal income due to loss of job.
The whole "lack of evidence" area is where I tend to see the most resistance within our field, so I'll try to counter the most common objection. I'm not saying that if we don't collect and analyze every single possible source and type of evidence on every single investigation of any type, that we're not doing our jobs. What I'm saying is that to the extent it is feasible and reasonable to do so, we need to collect and analyze the available and pertinent evidence in the most expedient manner, based on the informed risk appetite of the business.
There, I think that should start to set the stage for the next piece of the conversation. In our areas of lack of knowledge and lack of evidence, it's not necessarily a "bad" thing for them to exist one way or the other. What is a "bad" thing is to take certain courses of action without engaging the proper stakeholders in a risk conversation, so that they can make an informed decision on how doing one thing or another may negatively (or positively) impact the business. That's what risk management is all about, and now that we've seen that our actions can introduce new risk to the business, we need to start engaging the business on that level. A big piece of the puzzle here is that we, the DFIR contingent, are not really the ones to determine whether or not we only need to collect a certain type of evidence, or whether the lack of a certain type of evidence has a significant negative impact on an investigation. That's up to the business, and it's our job to inform them of the risks involved, so that they can weigh them accordingly in the context of the overall goals and needs of the business (to which we are likely not privy).
For example, in an IR scenario, we may not think it makes a lot of sense to image a bunch of system hard drives, due to the time it takes. We inform the business of the time and level of effort we estimate to be involved, and the impact of that distracting us from doing other things that may have more immediate relevance (such as dumping and analyzing RAM, or looking at pcaps from network monitoring). The business (executives, legal, etc) on their side, are aware of potential legal issues surrounding the situation, and know that if system-based evidence (of a non-volatile nature) is not preserved in a defensible fashion, the company could be tied up in legal battles for years. They determine that the cost/impact (aka, "risk") of ongoing legal battles is greater than the cost/impact (aka, "risk") of imaging the drives, so they provide the instruction to us. If we hadn't broached the subject and had a risk-based conversation with the appropriate stakeholders, we might have chosen based on our perspective, and incurred significant costs for the business and ourselves down the road.
So, am I saying we shouldn't make intelligent decisions ourselves? Should we do nothing until someone makes a choice for us? Please don't misunderstand me; by no means should we do nothing. But what we do should be tempered by the scenario we're in, and the inherent risk (to ourselves and others), juxtaposed against the risk appetite of those are paying us. After all, let's be honest - if a business is made to look bad or incur significant cost (whether through an incident response scenario, or some other investigation or legal action), most likely a "heads will roll" situation will arise. Professionally, it's our job to help ensure the business is well-informed, prepared, and protected from something like this happening; personally, it's our job to make sure it isn't our heads on the chopping block (C-levels may just move to another home, but if those who do the work get "branded" it may not be quite as easy). If you do a pentest engagement, what's the first thing you get? Your "get out of jail free" card, or a properly scoped and signed statement of work, which authorizes you to do the things you need in order to accomplish the mission. Think of what I'm saying from that angle: by making DFIR another risk topic, you're protecting yourself, your immediate boss/management, and the company/employer. There are other benefits as well - expectations are properly set, you have clear-cut direction, and can hopefully operate at peak efficiency. This keeps everyone happy (a very key point) and reduces cost; you gain visibility and insight into company needs and strategy, and are positioned to receive greater appreciation from the business (which can obviously be beneficial in a number of ways).
Now that we've wrapped up the risk association aspect, and everyone agrees with me 100%, we can frame in the two original areas of conversation - lack of KSAs and lack of evidence. I think the first is a given, but the second is the gray area for most folks. I've had numerous conversations around this concept, online and in person, and so far the puzzle analogy seems the easiest to digest. If you're putting together a 1000-piece puzzle without the box or picture of the completed puzzle (isn't that pretty much EVERY investigation you've ever done?), no matter how much you *think* you know what it is, you don't truly know until it's done. Attorneys and business management/executives want answers, and those can't be halfway formed, because they're making costly and potentially career-limiting decisions based upon what we say. So if you're only 25% done with the puzzle, you can't answer all the questions. If you limit yourself to 25% of the puzzle (or available evidence), or you're limited to that amount by other parties, you're limited in the information you can provide. If you're stuck with the 25% (as by forces outside your control), then you do the best you can, and inform the business - they might be able to apply pressure to get you access to more evidence (but if they don't know, they can't help you).
Let's look at the flip side of that briefly. If you're in an investigation (of whatever type), and there are 500 systems with 500 GB, 5400 RPM hard drives and only USB 2 connections; 10 TB of pcaps, 4 TB of logs from network appliances and systems, 20 servers spread across the country with 4 TB of local storage each and 400 TB combined network storage (where evidence might be), total RAM of 4 TB (plus pagefile and hiberfil), 2 people to get the work done and 1 week to do it, you're probably not going to be very successful. You'd really need near-unlimited resources and time, which just isn't the reality for any of us. But the reality also is that in this imaginary scenario, even with substantial resources, we'd still need to inform the business of the associated risks, so that they could help establish the true requirements, guidelines and timelines, and ultimately help us help them (note: it is sometimes necessary for us to guide the business through this process, to help them understand the point we're trying to get to). It really doesn't matter whether we're internal or external - our jobs put us in partnership with the business (unless the business wants us to lie or fabricate the truth, which becomes a completely different discussion that I won't get into here).
The goal is to make the best use of available evidence, time, and resources, to help the business answer the questions they need to address. If we have the necessary KSAs, and help the business understand the risks associated with the scope of an investigation, we can reach the end goal in a much more efficient manner than if we just work in a silo. I'd love to talk more; if you have any questions/comments/concerns, comment here or hit me up on twitter. Until then...
Think risk, and carry on.