網絡殺傷鏈

Intro

This is an important concept and I want to provide you with a quick overview of what are kill chains, what is threat modelling, why we do these things, and why we need them. This understanding is crucial in creating a stable and strong security posture.

One other thing to note is that all these frameworks are generally made to complement other frameworks. For example, the UKC – Unified Kill Chain – is made to be a complement to MITRE.

Cyber Kill Chain – what is it?

This term is a military term/concept that relates to an attack, in particular its structure. Lockheed Martin (security and aerospace company) is the one that established the Cyber Kill Chain in 2011, based on the aforementioned military concept. The idea of the framework is to define the steps adversaries are taking when attacking your organization. In theory, to be successful, the adversary would pass all the phases within the Kill Chain.

Our goal here is to understand what the Kill Chain means from an attacker’s perspective, so that we can put up our defences in place and either pre-emptively mitigate that, or disrupt their attacks.

Why do we need to understand the (Cyber) Kill Chain?

Understanding of the Cyber Kill Chain can help you protect against myriad of attacks, like ransomware, for example. It can also help you understand in what ways do APTs operate. Through this understanding, as a SOC Analyst, or Incident Responder, you can potentially understand the attacker’s goals and objectives by comparing it to the Kill Chain. It can also be used to find those gaps and remediate on missing controls.

The attack phases within the Cyber Kill Chain are:

• Reconnaissance
• Weaponization
• Delivery
• Exploitation
• Installation
• Command & Control
• Actions on Objectives (Exfiltration)

Reconnaissance

As we all know, this means searching for and collecting the information about system(s). In this phase, our adversaries are doing their planning. This is also where OSINT comes in, and is usually the first step an adversary will take, before going further down the chain. They will try and collect any possible piece of info on our organization, employees, emails, phones, you name it.

This can be done, for example, through email harvesting – process of collecting email addresses from online (public, paid, or free) services. These can further be used for a phishing campaign, or anything else.

Within the recon step, they also might collect the socials of the org’s employees, especially if some employee in particular might seem of interest or is a bit more of an easier target. All this information goes into the mix and is nothing new. First step – Recon.

Weaponization

After the initial recon phase, our adversary goes on to create their weapons! Usually, this entails some sort of malware/exploit combination bundled into a payload of sorts. Some adversaries will straight up buy the malware on the Darkweb marketplaces, but some more sophisticated attackers, as well as the APTs, will usually write their own malware. This is advantageous as it might actually evade your detection systems.

They can go on about this in numerous ways, but some examples might include them creating a malicious MS Office document with bad macros or VBA scripts, they could also use Command & Control techniques so that your affected machine calls to the Command server for more of those malicious payloads. (Yikes!) Or, they could add a backdoor, some other type of malware, or anything really.

Delivery

This step entails the attacker choosing a way to deliver the payload/malware to their victim. There are many options here, but in general, the most used one is good old phishing email.

With a phishing email that’s sent after the successfully completed reconnaissance phase, the attacker can target a specific person (spearphishing), or a group of employees at your organization. Within the email would be the embedded payload.

Other ways to distribute the payload may include the attackers planting infected USBs in public places, like parking lots, the streets, etc. Or, they could use a so-called watering hole attack which basically aims at a specific group of people by sending them to an attacker controlled website, by redirecting them to that site off a site they generally use but is now compromised by the attacker.

The attacker exploits the website, and then somehow tries to get the unsuspecting users to browse to the site where the victim basically downloads the malware/payload unintentionally.

Exploitation

Before finally getting access to our systems, the attackers need to carry out an actual exploit. Suppose the previous steps worked and the user downloaded or somehow ran the malicious payload, the attacker is ready for the next steps… or whatever’s in between! They can try to move laterally, get to your server, escalate privileges, anything goes.

This step boils down to

• Victim opening the malicious file, thus triggering the exploitation
• The adversary exploits our systems through a server, or some other way
• They use a 0 day exploit

Whatever the vector, it comes down to them exploiting our systems and gaining access.

Installation

This step comes after the exploitation and it usually pertains to the adversary trying to keep a connection of sorts to our system. This can be achieved in many ways, for example, they might try to install the backdoor on the compromised machine, or they could modify our services, they could also install a web shell on the webserver, or anything else that helps them achieve persistence. This is key for the Installation phase.

The persistent backdoor is what will let the attacker interact and access our systems that were already compromised.

In this phase, they also might try to cover their tracks from your blue team by trying to make the malware look as if it was a legitimate app/program.

Command & Control

The Command & Control, also known as C2, C2 beaconing, or C&C is the penultimate part, and this is where the adversary uses the previously installed malware on the victim’s device to control the device remotely. This is usually built into the malware itself, and it has some sort of logic through which it calls back home to its Control server.

As the infected device calls back to the C2 server, the adversary now has full control over the compromised device. Remotely!

The most used C2 channels these days are:

• HTTP protocol 80, HTTPS port 443 – HTTPS is interesting as it can help hide within the encrypted stream and it can potentially help the malicious traffic evade firewalls
• DNS – the infected host will make constant DNS queries calling to its C2 server

An interesting fact – In the past, adversaries used IRC to send C2 traffic (beaconing), but nowadays it’s became obsolete as this type of bad traffic is much more easily detectable by the modern/current security solutions.

Actions on Objectives (Exfiltration)

This is your exfiltration (or exfil) step, where the adversary tries to gather all the goodies they just stole, so, user credentials, messing with the backups and/or shadow copies, corrupt/delete/overwrite/exfiltrate data. They can also escalate to domain admin, for the keys to the kingdom, or move laterally through the organization. They could also try to find vulnerabilities of your software internally, and much more.

This step depends on their specific goals/objectives, and is where all the action will happen, thus actions on objectives.

Conclusion

I hope I’ve managed to give a brief overview of this incredibly important concept. I will cover it a bit more in the future, but for now, I felt like this was a good (traditional) start. I do hope to cover the Unified Kill Chain soon, though. So – stay tuned!

Ps: you’ll notice there are a couple of other frameworks/variations aside from the Cyber Kill Chain, and I will try to explain the distinctions. Just remember these are models/methodologies and there’s no silver bullet. They should be used in conjunction with other security controls.

Image source – https://www.lockheedmartin.com/en-us/capabilities/cyber/cyber-kill-chain.html

Cover image by Linus Sandvide

#kill-chain #cyber #C2 #threat-modelling