Hackers Abuse EDR Free Trials to Bypass Endpoint Protection

Cybersecurity researchers have uncovered a concerning new attack vector where threat actors are exploiting free trials of endpoint detection and response (EDR) software to disable existing security protections on targeted systems.

This technique, dubbed “BYOEDR” (Bring Your Own EDR), represents a sophisticated method for attackers to bypass enterprise security measures using legitimate tools.

Discovery and Technical Details

The vulnerability was first highlighted by security researcher BushidoToken on social media, who observed threat actors actively abusing certain EDR products in real-world attacks.

Following this alert, researchers conducted extensive testing at BSides Albuquerque and made several alarming discoveries about the ease with which attackers can weaponize security software against itself.

The research team found that obtaining free trials of some EDR and antivirus products requires minimal validation, making it trivially easy for malicious actors to access these powerful tools.

More concerning, they demonstrated that one EDR product under attacker control can effectively disable another legitimate EDR installation on the same system.

In their testing, researchers successfully used Cisco Secure Endpoint (formerly AMP) to disable both CrowdStrike Falcon and Elastic Defend without triggering any alerts or generating telemetry beyond the host going offline.

The technique involves removing security exclusions and adding the hash of the existing EDR software as a blocked application, effectively turning the security tool into a weapon against competing products.

What makes this attack vector particularly dangerous is its ability to bypass tamper protection features that are specifically designed to prevent EDR manipulation.

While the technique requires local administrator access on the target system, it represents a lower-complexity approach compared to traditional EDR evasion methods like Bring Your Own Vulnerable Driver (BYOVD) attacks or DLL-unhooking techniques.

The attack fits into the post-compromise phase of cyber operations, occurring after initial access and privilege escalation but before lateral movement and data collection.

For at least one vendor, ESET, researchers found it possible to install an attacker-controlled instance that could hijack control from an existing legitimate installation.

This EDR abuse technique aligns with a broader trend of attackers leveraging legitimate administrative tools for malicious purposes.

The 2024 CrowdStrike Threat Hunting Report documented a 70% year-over-year increase in remote management and remote access tool abuse, while Arctic Wolf reported RMM tools were involved in 36% of their investigated cases.

These legitimate tools are particularly attractive to attackers because they are trusted, properly signed with valid certificates, and far less likely to trigger security alerts compared to traditional malware.

Security experts recommend implementing application control policies, custom behavioral indicators, and application-aware firewalls to block unauthorized RMM, AV, and EDR tools.

Organizations should also focus on fundamental security practices including proper network segmentation, environment hardening, consistent patching, and limiting local administrator privileges through solutions like Local Administrator Password Solution (LAPS).

Vendors are being urged to implement stronger validation processes for free trials and ensure that new installations cannot hijack existing agent control from legitimate tenants.

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