The anatomy of an endpoint attack

Cyberattacks are becoming increasingly sophisticated as tools and services on the dark web – and even the surface web – enable low-skill threat actors to create highly evasive threats. Unfortunately, most of today’s modern malware evades traditional signature-based anti-malware services, arriving to endpoints with ease. As a result, organizations lacking a layered security approach often find themselves in a precarious situation. Furthermore, threat actors have also become extremely successful at phishing users out of their credentials or simply brute forcing credentials thanks to the widespread reuse of passwords.

A lot has changed across the cybersecurity threat landscape in the last decade, but one thing has remained the same: the endpoint is under siege. What has changed is how attackers compromise endpoints. Threat actors have learned to be more patient after gaining an initial foothold within a system (and essentially scope out their victim).

Take the massive Norsk Hydro ransomware attack as an example: The initial infection occurred three months prior to the attacker executing the ransomware and locking down much of the manufacturer’s computer systems. That was more than enough time for Norsk to detect the breach before the damage could done, but the reality is most organization simply don’t have a sophisticated layered security strategy in place.

In fact, the most recent IBM Cost of a Data Breach Report found it took organizations an average of 280 days to identify and contain a breach. That’s more than 9 months that an attacker could be sitting on your network planning their coup de grâce.

So, what exactly are attackers doing with that time? How do they make their way onto the endpoint undetected?

It usually starts with a phish. No matter what report you choose to reference, most point out that around 90% of cyberattacks start with a phish. There are several different outcomes associated with a successful phish, ranging from compromised credentials to a remote access trojan running on the computer. For credential phishes, threat actors have most recently been leveraging customizable subdomains of well-known cloud services to host legitimate-looking authentication forms.

The above screenshot is from a recent phish WatchGuard Threat Lab encountered. The link within the email was customized to the individual recipient, allowing the attacker to populate the victim’s email address into the fake form to increase credibility. The phish was even hosted on a Microsoft-owned domain, albeit on a subdomain (servicemanager00) under the attacker’s control, so you can see how an untrained user might fall for something like this.

In the case of malware phishes, attackers (or at least the successful ones) have largely stopped attaching malware executables to emails. Most people these days recognize that launching an executable email attachment is a bad idea, and most email services and clients have technical protections in place to stop the few that still click. Instead, attackers leverage dropper files, usually in the form of a macro-laced Office document or a JavaScript file.

The document method works best when recipients have not updated their Microsoft Office installations or haven’t been trained to avoid macro-enabled documents. The JavaScript method is a more recently popular method that leverages Windows’ built-in scripting engine to initiate the attack. In either case, the dropper file’s only job is to identify the operating system and then call home and grab a secondary payload.

That secondary payload is usually a remote-access trojan or botnet of some form that includes a suite of tools like keyloggers, shell script-injectors, and the ability to download additional modules. The infection isn’t usually limited to the single endpoint for long after this. Attackers can use their foothold to identify other targets on the victim’s network and rope them in as well.

It’s even easier if the attackers manage to get hold of a valid set of credentials and the organization hasn’t deployed multi-factor authentication. It allows the threat actor to essentially walk right in through the digital front door. They can then use the victim’s own services – like built-in Windows scripting engines and software deployment services – in a living-off-the-land attack to carry out malicious actions. We commonly see threat actors leverage PowerShell to deploy fileless malware in preparation to encrypt and/or exfiltrate critical data.

The WatchGuard Threat Lab recently identified an ongoing infection while onboarding a new customer. By the time we arrived, the threat actor had already been on the victim’s network for some time thanks to compromising at least one local account and one domain account with administrative permissions. Our team was not able to identify how exactly the threat actor obtained the credentials, or how long they had been present on the network, but as soon as our threat hunting services were turned on, indicators immediately lit up identifying the breach.

In this attack, the threat actors used a combination of Visual Basic Scripts and two popular PowerShell toolkits – PowerSploit and Cobalt Strike – to map out the victim’s network and launch malware. One behavior we saw came from Cobalt Strike’s shell code decoder enabled the threat actors to download malicious commands, load them into memory, and execute them directly from there, without the code ever touching the victim’s hard drive. These fileless malware attacks can range from difficult to impossible to detect with traditional endpoint anti-malware engines that rely on scanning files to identify threats.

Elsewhere on the network our team saw the threat actors using PsExec, a built in Windows tool, to launch a remote access trojan with SYSTEM-level privileges thanks to the compromised domain admin credentials. The team also identified the threat actors attempts to exfiltrate sensitive data to a DropBox account using a command-line based cloud storage management tool.

Fortunately, they were able to identify and clean up the malware quickly. However, without the victim changing the stolen credentials, the attacker could have likely re-initiated their attack at-will. Had the victim deployed an advanced Endpoint Detection and Response (EDR) engine as part of their layered security strategy, they could have stopped or slowed the damage created from those stolen credentials.

Attackers are targeting businesses indiscriminately, even small organizations. Relying on a single layer of protection simply no longer works to keep a business secure. No matter the size of an organization, it’s important to adopt a layered security approach that can detect and stop modern endpoint attacks. This means protections from the perimeter down to the endpoint, including user training in the middle. And, don’t forget about the role of multifactor authentication (MFA) – could be the difference between stopping an attack and becoming another breach statistic.