What are Living off the Land attacks?

According to SANS security researcher David Brown, Living off the Land (LOTL) attacks describe "a cyberattack in which intruders use legitimate software and functions available in the system to perform malicious actions on it." Rather than deploying custom malware that might trigger security alerts, threat actors leverage pre-installed system tools and legitimate software to achieve their malicious objectives, making detection significantly more challenging for traditional security solutions.

Understanding Living off the Land attacks

Living off the Land attacks represent a sophisticated evolution in cybercriminal tactics. Just as surviving off the land in the physical world means using only naturally available resources, LOTL attacks leverage pre-existing system tools and legitimate software to conduct malicious activities. This approach allows attackers to bypass traditional security measures and disguise their actions as legitimate system processes.

According to the Cybersecurity and Infrastructure Security Agency (CISA), which references the LOLBAS (Living Off The Land Binaries and Scripts) Project, over 100 legitimate Microsoft programs can be abused in LOTL attacks. This extensive list demonstrates how pervasive the threat has become, as cybercriminals have systematically identified ways to weaponize tools that system administrators use daily for legitimate purposes.

The growing threat landscape

"Increasingly, attackers are relying on trusted Microsoft programs to carry out attacks against individuals and organizations," states David Brown. This observation is concerning for healthcare organizations, which face unique vulnerabilities due to their complex, interconnected systems and often limited cybersecurity budgets.

A 2024 report from the FBI and HHS documented sophisticated LOTL attacks targeting U.S. healthcare organizations, revealing how threat actors gained initial access through social engineering tactics. The attackers called IT help desks posing as employees, triggering password resets and bypassing multi-factor authentication. Once inside, they amended Automated Clearing House (ACH) forms to divert legitimate payments to attacker-controlled accounts, demonstrating the financial impact these attacks can have.

Common Living off the Land techniques

Attackers employ various LOTL techniques to compromise systems:

• PowerShell exploitation: This Windows scripting tool, designed for system administration, is frequently abused to execute commands, download malicious code, and automate tasks without triggering security alerts.
• Binary planting: Also known as DLL hijacking, attackers place malicious code where vulnerable applications will unknowingly load and execute it, exploiting the trust relationship between applications and system libraries.
• Registry manipulation: Threat actors modify Windows registry keys to maintain persistence, ensuring their code runs at system startup while appearing as legitimate system processes.
• Fileless malware: Malicious code resides only in memory rather than on disk, leaving no traditional file signatures for antivirus software to detect, making forensic analysis challenging.
• WMI abuse: Windows Management Instrumentation, designed for system administration, is repurposed for remote command execution and lateral network movement across compromised networks.

The 2020 SolarWinds supply chain attack exemplifies the potential of LOTL techniques. According to Google Cloud's analysis, threat actors compromised the SolarWinds Orion software update mechanism to distribute malware called SUNBURST to thousands of organizations worldwide.

Google described this as "some of the best operational security that FireEye has observed in a cyber attack, focusing on evasion and leveraging inherent trust." The attackers demonstrated exceptional tradecraft by setting hostnames on their command infrastructure to match legitimate hostnames within victim environments, allowing them to blend in seamlessly. They used IP addresses from the same country as their victims and employed temporary file replacement techniques, replacing legitimate utilities with malicious ones, executing their payload, then immediately restoring the original files.

The SUNBURST backdoor remained dormant for up to two weeks before activating, then masqueraded its communications as the legitimate Orion Improvement Program (OIP) protocol. This sophisticated approach allowed the attackers to operate undetected in victim networks for extended periods, demonstrating how LOTL techniques enable persistent, stealthy access to critical systems.

FAQs

What is PowerShell?

PowerShell is a powerful command-line tool and scripting language built into Windows that allows administrators to automate tasks and manage systems. 

What is fileless malware?

Fileless malware is malicious code that runs entirely in a computer's memory (RAM) rather than being saved as a file on the hard drive. This makes it harder to detect because traditional antivirus software primarily scans files on disk. 

What is lateral movement?

Lateral movement refers to techniques attackers use to move from one compromised system to another system within the same network. Once they gain initial access, attackers explore the network to find valuable data or gain higher privileges.

Go deeper: Lateral movement explained: How hackers navigate networks undetected