What we today define “ransomware” at the beginning were basically screen lockers demanding a ransom from the victim (“Your PC contains illegal content and cannot be used …“).
In relation to the increasing revenues they are able to generate, in recent years they have become one of the fastest growing classes of malicious software in the cyber threat landscape.
Lately, moreover, almost all of the interventions and articles on “cyber” topics were related to this category of malware as a result of a specific attack against Colonial Pipelines Inc. which caused countless economic losses and inconveniences of any kind in the States.
In face of first rivers of ink spilled on the incident itself and then on the group responsible for the attack (- note it was one of the group’s affiliates and not the same dev team of the #DarkSide ransomware -) they are not missing, here and there, articles / advice / posts by experts on how to defend against this type of malware.
The plethora of suggestions given, however, in my opinion have rarely been placed within a strategic context and almost always indicated as a list of specific actions to be performed.
The individual items of these lists, although singularly impeccable from a theoretical point of view (such as “installing a good antivirus” and “applying risk management processes“), can be difficult to apply in practice if not placed in a well-defined context that pursue a specific purpose; this purpose should the contrast and mitigation of extortion-oriented attacks and much more generally the enhancement of one’s defensive capabilities.
Finally, considering the famous phrase – “It is not possible to be 100% protected from malicious code” – it is also clear that a valid defensive solution cannot be based exclusively on the adoption of the latest AV / EDR technologies (more or less sophisticated) nor much less on tricks and / or tips of the last minute.
Implementing a good defense program against these threats is undoubtedly an active and continuous process over time that involves the strengthening of at least five (5) internal capabilities.
Prevention: prevent the exploitation of infrastructure weaknesses and / or vulnerabilities through processes for updating, hardening and control of public information (social networks, public managers / employees profiles, job descriptions …) Technically speaking, in some cases, prevention could also mean adopting alternative technologies to those already in place and normally used, for example, for remote access services (VPN / RDP) in order to totally eliminate the growing risks due to the greater attention of criminal groups against them (0day research, 1 day exploit and theft / sale of access credentials on clearnet / darknet). Their potential compromise, in fact, could be catastrophic for the environment to be protected and provide an advantage that is difficult to recover on a defensive level as these services are often designed to interface directly with corporate intranets.
Detection and Protection: represents the ability to protect your assets from potentially adverse events by acquiring the ability to detect and contain a threat. As for the malicious code, the protection of your assets certainly includes the adoption of an AV / EDR, execution prevention systems, sandboxes etc.etc.
Resistance: indicates the ability to face and / or minimize the effects of an unknown or particularly stealthy threat and which has a high possibility of representing a concrete risk. It involves the implementation of concepts such as the separation of environments, the reduction of the potential attack surface, the identification of critical services and more stringent access control to them, etc. etc.
Resilience: indicates the ability to recover after an accident. Knowledge (SA – Situational Awareness): it means clearly understanding what to defend against in relation to our perimeter as well as the tactics and procedures implemented by the opponents and the consequent adoption of a defense strategy.
Knowledge (SA – Situational Awareness): it means clearly understanding what one must defend against in relation to our perimeter as well as the tactics and procedures implemented by the adversaries and a consequent adoption of a defense strategy.
The Covid-19 pandemic has been very useful for the “ransomware” business. In general the higher revenues of many criminal groups (tripled, according to some estimates, compared to the pre-covid period) are due to the inability of many organizations to adapt to a de-centralized work model after a large percentage of their the workforce begun to operate outside a defined perimeter (the classic corporate one).
However, in many cases, it should be noted that the extension of the attack surface as a direct consequence of the new “smart-workers” not actually created a “new” problem from scratch but has often magnified one that was present even previously. This problem is mainly due to the lack of equipment (not only in the technological field but also in the procedural and internal policies ones) with which many companies fight these threats.
The most typical and widespread weakness observed during the analysis of some incidents was to focus (or limit) these defense on few points compared to the five (5) listed above. Closely related to what the “classic” cyber-security industry proposes, very often the one and only line of defense is delegated to AntiVirus / EDR and “Monitoring Operations“, thus concentrating all the contrast strategy in the already described capacity of “Detection and Protection“.
In consideration of the fact that even the most modern anti-malware solutions available on the market cannot guarantee detection rates even close to 100% (without considering the context on the basis of which an adversary arrives to operate within our perimeter) itìs evident that relying exclusively on them may not be enough.
Survival vs Kill Chain:
All the intrusions that arrive at a ransom request have effectively closed the so-called “Kill-chain”. The kill-chain virtually represents a series of steps (or rings), precisely, concatenated, and in general, simplifying, they are:
1. Information gathering
2. First access and early-stage payload delivery
3. Lateral movement
4. Late-stage payload delivery
Closing this chain often means, for the victim, having to pay an expensive ransom to get back its data and documents. An effective contrast strategy will therefore provide for the direct mitigation of the potential risks deriving from each single phase (or ring) of this kill-chain, directing, with a more strategic vision, one’s work towards the five (5) points identified before.
Information Gathering: In this phase, attackers seek and hunt potential victims by acquiring information about them. While only some time ago the approach to choice seemed to be quite casual and a direct consequence of the general external posture of the organization to hit (in the sense that robbing a shop is generally easier than robbing a bank) now the trend seems to be moving towards a much more targeted decision, so as to be able to ask for very substantial ransoms once the operation succeed. Under the heading of “Prevention“, fall the set of activities aimed at not exposing the side to such attacks by trying to contain the information released (voluntarily or not) on social networks and public profiles of the company. In this regard, Security Awareness programs are particularly useful. Information sources (threat intelligence) designed to increase the levels of Situational Awareness of the staff in charge of network protection can also be particularly useful.
First Access / Early-Stage payload delivery: In this phase, the attacker is able to obtain a first access to the perimeter. In order to make their life as difficult as possible it is necessary to correctly apply hardening and patching programs to the systems. Technically limiting the potential attack surface, applying multiple authentication systems, blocking the execution of macros and scripting languages that are not strictly necessary, checking permissions, logically limiting the communications of internal workstations are all useful factors for an Incident Prevention strategy. If the attacker still manages to deliver a first-stage payload and therefore to obtain a first access to our infrastructure, the adoption of policies aimed at obtaining greater visibility regarding what is happening (for example: alerts on login credentials anomalies, alerts on changes to accounts in the AD – Active Directory -, alerts on malicious DNS resolutions, alerts on network flow anomalies – Firewall Logs -, alerts on IDS / IPS events and so on…) is useful to strengthen our Detection and Protection skills. EDR / AV and SIEM support these skills as well.
Lateral movement: In this phase, the attacker managed to effectively compromise one or more machines inside our infrastructure and aims at expanding his/her control. If the defenses put in place up to now have proved ineffective, a further protective barrier capable of mitigating what is in place could be represented by the application of strong network segmentation policies of the environments. A further critical factor that can significantly increase our Resistance skills is the application of Behavior Analytics Systems.
Late-stage payload delivery: If the strategies applied so far have proved particularly ineffective in combating a so advanced and persistent adversary, we could suffer the effects of the last phase of a ransomware-kill-chain, that is the release of the last stage payload, the one that will probably be in charge of encrypting our data and information. Most likely the attacker already got the full control of several internal machines and probably also obtained “admin–grade” credentials. Based on my personal experience, therefore, if we are at this point there is little chance that the Detection and Protection systems can effectively mitigate the course of events. The best defense at this point is to have a good backup of all data, files, applications and any other critical resources. These backups must obviously be isolated from other systems.
The ransomware business is particularly profitable. Considering the revenues it generates, it’s possible to assume possible to assume much more frequent and sophisticated attacks. The application of defensive measures in the various stages of the kill-chain, however, can reduce the risk of a full data loss (and to rely exclusively on negotiations with criminals to recover them).