Endpoint Advanced Protection: The Evolution of Prevention
As we discussed in our last post, there is a logical lifecycle which you can implement to protect endpoints. Once you know what you need to protect and how vulnerable the devices are, you try to prevent attacks, right? Was that a snicker? You’ve been reading the trade press and security marketing telling you prevention is futile, so you’re a bit skeptical. You have every right to be – time and again you have had to clean up ransomware attacks (hopefully before they encrypt entire file servers), and you detect command and control traffic indicating popped devices frequently. A sense of futility regarding actually preventing compromise is all too common. Despite any feelings of futility, we still see prevention as key to any Endpoint Protection strategy. It needs to be. Imagine how busy (and frustrated) you’d be if you stopped trying to prevent attacks, and just left a bunch of unpatched Internet-accessible Windows XP devices on your network, figuring you’d just detect and clean up every compromise after the fact. That’s about as silly as basing your plans on stopping every attack. So the key objective of any prevention strategy must be making sure you aren’t the path of least resistance. That entails two concepts: reducing attack surface, and risk-based prevention. Shame on us if devices are compromised by attacks which have been out there for months. Really. So ensuring proper device hygiene on endpoints is job one. Then it’s a question of deciding which controls are appropriate for each specific employee (or more likely, group of employees). There are plenty of alternatives to block malware attacks, some more effective than others. But unfortunately the most effective controls are also highly disruptive to users. So you need to balance inconvenience against risk to determine which makes the most sense. If you want to keep your job, that is. “Legacy” Prevention Techniques It is often said that you can never turn off a security control. You see the truth in that adage when you look at the technologies used to protect endpoints today. We carry around (and pay for) historical technologies and techniques, largely regardless of effectiveness, and that complicates actually defending against the attacks we see. The good news is that many organizations use an endpoint protection suite, which over time mitigates the less effective tactics. At least in concept. But we cannot fully cover prevention tactics without mentioning legacy technologies. These techniques are still in use, but largely under the covers of whichever endpoint suite you select. Signatures (LOL): Signature-based controls are all about maintaining a huge blacklist of known malicious files to prevent from executing. Free AV products currently on the market typically only use this strategy, but the broader commercial endpoint protection suites have been supplementing traditional signature engines with additional heuristics and cloud-based file reputation for years. So this technique is used primarily to detect known commodity attacks representing the low bar of attacks seen in the wild. Advanced Heuristics: Endpoint detection needed to evolve beyond what a file looks like (hash matching), paying much more attention to what malware does. The issue with early heuristics was having enough context to know whether an executable was taking a legitimate action. Malicious actions were defined generically for each device based on operating system characteristics, so false positives (notably blocking a legitimate action) and false negatives (failing to block an attack) were both common – a lose/lose scenario. Fortunately heuristics have evolved to recognize normal application behavior. This dramatically improved accuracy by building and matching against application-specific rules. But this requires understanding all legitimate functions within a constrained universe of frequently targeted applications, and developing a detailed profile of each covered application. Any unapproved application action is blocked. Vendors need a positive security model for each application – a tremendous amount of work. This technique provides the basis for many of the advanced protection technologies emerging today. AWL: Application White Listing entails implementing a default deny posture on endpoint devices (often servers). The process is straightforward: Define a set of authorized executables that can run on a device, and block everything else. With a strong policy in place, AWL provides true device lockdown – no executables (either malicious or legitimate) can execute without explicit authorization. But the impact to user experience is often unacceptable, so this technology is mostly restricted to very specific use cases, such as servers and fixed-function kiosks, which shouldn’t run general-purpose applications. Isolation: A few years ago the concept of running apps in a “walled garden” or sandbox on each device came into vogue. This technique enables us to shield the rest of a device from a compromised application, greatly reducing the risk posed by malware. Like AWL, this technology continues to find success in particular niches and use cases, rather than as a general answer for endpoint prevention. Advanced Techniques You can’t ignore old-school techniques, because a lot of commodity malware still in circulation every day can be stopped by signatures and advanced heuristics. Maybe it’s 40%. Maybe it’s 60%. Regardless, it’s not enough to fully protect endpoints. So endpoint security innovation has focused on advanced prevention and detection, and also on optimizing for prevalent attacks such as ransomware. Let’s unpack the new techniques to make sense of all the security marketing hyperbole getting thrown around. You know, the calls you get and emails flooding your inbox, telling you how these shiny new products can stop zero-day attacks with no false positives and insignificant employee disruption. But we don’t know of any foolproof tools or techniques, so we will focus the latter half of this series on detection and investigation. But in fairness, advanced techniques do dramatically increase the ability of endpoints to block attacks. Anti-Exploit/Exploit Prevention The first major category of advanced prevention techniques focus on blocking exploits before the device is compromised. Security research has revealed a lot of how malware actually compromises endpoints at a low level, so tools now look for those indicators. 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