ClickFix: How Attackers Exploited finger.exe for Stealthy Network Access in 2023
In November 2023, organizations reported a wave of Living-off-the-Land (LotL) attacks known as ClickFix, in which adversaries abused the legacy finger.exe utility on Windows systems. Attackers exploited finger.exe to retrieve and execute malicious scripts by leveraging the finger protocol over TCP port 79, bypassing endpoint security tools that are often tuned for more common protocols. The technique allowed attackers to maintain stealthy communications and initial access, exposing corporate environments where outbound traffic controls were inadequate. No major ransomware group claimed responsibility, but the campaign highlighted increasing sophistication in LotL exploitation, putting enterprises at risk of lateral movement and data exfiltration. This incident is highly relevant given the resurgence of attackers abusing built-in OS utilities to evade detection, as well as increased regulatory scrutiny over encrypted and segmented internal network traffic. Organizations must reevaluate their defenses against legacy protocol abuse.
Kill Chain
