Defending Against Supply Chain Attacks

In this post, I will discuss the concepts of supply chain attacks and some thoughts around defending against them.

What Is A Supply Channel Attack?

The recent ransomware attack through Kaseya made the news but the concept of a supply chain attack isn’t new at all. Without doing any research I can think of two other examples:

  • SolarWinds: In December 2020, attackers used compromised code in SolarWinds monitoring solutions to compromise customers of SolarWinds.
  • RSA: In 2011, the Chinese PLA (or hackers sponsored by them) compromised RSA and used that access to attack customers of RSA.

What is a supply chain attack? It’s pretty hard to break into a network, especially one that has hardened itself. Users can be educated – ok, some will never be educated! Networks can be hardened and micro-segmented. Identity protections such as MFA and threat detection can be put in place.

But there remains a weakness – or several of them. There’s always a way into a network – the third party! Even the most secure network deployments require some kind of monitoring system – something where a piece of software is deployed onto “every VM”.  Or there’s some software vendor that’s deep into your network that has openings all over the place. Those are your threats. If an attacker compromises the software from one of those vendors then they will get into your network during your next update and they will use the existing firewall holes & permissions that are required by the software to probe, spread, and attack.

Protection

You still need to have your first lines of defense, ideally using tools that are designed for protection against advanced persistent threats – not your regular AV package, dumby:

  1. Identity
  2. Email
  3. Firewall
  4. Backup with isolated offline storage protected by MFA

That’s a start, but, but a supply chain attack bypasses all that by using existing channels to enter your network as if it is from a trusted source – because the attack is embedded in the code from a trusted source.

Micro-Segmentation

The first step should be micro-segmentation (AKA multi-segementation). No two nodes on your network should be able to communicate unless:

  1. They have to
  2. They are restricted to the required directions, protocols, and ports.
  3. That traffic passes through a firewall – and ideally several firewalls.

In Microsoft Azure, that means using:

  • A central firewall, in the form of a network firewall and/or web application firewall (Azure or NVA). This firewall controls connections between the outside world and your workloads, between your workloads, and importantly from your workloads to the outside world (prevents malware from talking to its human controller).
  • Network Security Groups at the subnet level that protect the subnet and even isolate nodes inside the subnet (use a custom Deny All rule because the default Deny All rule is useless when you understand the logic of how it works).
  • Resource firewalls – that’s the guest OS firewall and Azure resource firewalls.

If you have a Windows ADDS domain, use Group Policy to force the use of Windows Firewall – lazy admins and those very same vendors that will be the channel of attack will be the first to attempt to disable the firewall on machines that they are working on.

For Azure resources, consider the use of Azure Policy to force/audit the use of the firewalls in your resources and a default route to 0.0.0.0/0 via your central firewall.

An infrastructure-as-code approach to the central firewall (Azure Firewall) and NSGs brings documentation, change control, and rollback to network security.

Security Monitoring

This is where most organisations fail, and even where IT security officers really don’t get it.

Syslog is not security monitoring. Your AV is not security monitoring. You need something bigger, that is automated, and can filter through the noise – I regularly use the term “be your Neo to read the Matrix”. That’s because even in a small network, there is a lot of noise. Something needs to filter through that noise and identity the threats.

For example, there’s a lot of TCP 445 connection attempts coming from one IP address. Or there are lots of failed attempts to sign in as a user from one IP address. Or there are lots of failed connections logged by NSG rules. Or even better – all of the above. These are the sorts of things that malware that is attempting to spread will do. This is the sort of work that Azure Sentinel is perfect for – Sentinel connects to many data sources, pulls that data to a central place where complex queries can be run to look for threats that a human won’t be able to do. Threats can create incidents, incidents can trigger automated flows to eliminate the noise, and the remaining incidents can create alerts that humans will act upon.

But some malware is clever and not so noisy. The malware that hit the HSE (the Irish national health service) uses a lot of manual control to quietly spread over a very long time. Restricting outbound access to the Internet to just the required connections for business needs will cripple this control mechanism. But there’s still an automated element to this malware.

Other things to implement in Azure will include:

  • IDPS: An intrusion detection & prevention in the firewall, for example Azure Firewall Premium. When known malware/attack flows pass through the firewall, the firewall can log an alert or alert/deny the flows.
  • Security Center: Enabling Security Center “Azure Defender” (the tier previously known as the Azure Security Center Standard) provides you with oodles of new features, including some endpoint protections that are very confusingly packaged and licensed by Microsoft.

Managed Services Providers

MSPs are a part of the supply chain for their customers. MSP staff typically have credentials that allow them into many customer networks/services. That makes the identities of those staff very valuable.

A managed service provider should be a leader in identity security process, tooling, and governance. In the Microsoft world, that means using Azure AD Premium with MFA enabled for all staff. In the Azure world, Lighthouse should be used to gain access to customers’ cloud implementations. And that access should be zero-trust, powered by Privileged Identity Management (PIM).

Oh Cr@p!

These attackers are not script kiddies. They are professional organisations with big budgets, very skilled programmers and operators, and a lot of time and will. They know that with some persistent effort targeting a vendor, they can enter a lot of networks with ease. Hitting a systems management company, or more scarily, a security vendor, reaps BIG rewards because we invest in these products to secure our entire networks. The other big worry is those vendors that are deeply embedded with certain verticals such as finance or government. Imagine a vendor that is in every branch of a national government – one successful attack could bring down that entire government after  a wave of upgrades! Or hitting a well known payment vendor could open up every bank in the EU.

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