A novel social engineering marketing campaign, dubbed ClickFix, has been recognized, which cleverly employs an previous Home windows command-line device, finger.exe, to put in malware on victims’ programs.
This assault begins with a misleading CAPTCHA verification web page, tricking customers into working a script that initiates the an infection course of.
The method has been in use since at the least November 2025 and continues to be a persistent risk.
The assault’s reliance on the finger protocol, a legacy networking device for retrieving person data, is a novel attribute.
Risk actors are abusing this seemingly innocent utility to fetch malicious payloads from distant servers.
This methodology permits the attackers to bypass some safety measures that aren’t configured to observe or block visitors over the finger protocol’s designated TCP port 79.
Web Storm Heart analysts/researchers famous this exercise and have been monitoring two outstanding campaigns using this method: KongTuke and SmartApeSG.
Faux CAPTCHA pages
Each campaigns leverage faux CAPTCHA pages to lure customers into executing the preliminary finger command, demonstrating a shared methodology.
Faux CAPTCHA web page (Supply – Web Storm Heart)
The continued use of this tactic highlights its effectiveness in environments the place legacy protocols aren’t adequately secured.
Upon execution, the finger command contacts a command-and-control server. For example, the KongTuke marketing campaign makes use of a command like finger gcaptcha@captchaver[.]prime.
Discovering finger visitors utilizing the finger filter in Wireshark (Supply – Web Storm Heart)
The server responds with a PowerShell command containing Base64 encoded textual content, which then executes on the person’s machine to hold out additional malicious actions.
The SmartApeSG marketing campaign operates equally, utilizing a command reminiscent of finger [email protected][.]108 to retrieve a script.
Textual content returned from the server in response to the finger command (Supply – Web Storm Heart)
This script then downloads and executes a malicious file, which exhibits the script retrieving a file named yhb.jpg that accommodates the malicious payload.
This multi-stage course of permits the malware to determine a foothold on the compromised system.
Whereas company networks with express proxies could block TCP port 79, many programs stay weak if this port will not be explicitly blocked, making these assaults a continued concern for community directors.
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