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Gruel is a Microsoft Windows worm first observed in 2003, also referred to by F-Secure as Fakerr. It is detected by some vendors as W32.Gruel@mm and W32/Gruel-D. The worm targets Windows 9x, Windows ME, Windows 2000, and Windows XP, and is described as approximately 102,400 bytes in size. It spreads via email attachments and file-sharing networks, often using varied filenames and masquerading as a security update from Microsoft or, in some variants, a Symantec security tool or update. When executed, it installs itself and displays a fake Windows Error Reporting dialog that cannot be moved or closed. If the user clicks "Send Error," Gruel mass-mails itself to all of the user’s contacts and then shows fictitious technical details. If the user clicks "Send and Close," it terminates or disables Windows Explorer, ejects the CD/DVD drive, and opens multiple Control Panel items, then presents another uncloseable dialog with "Retry" and "Cancel" buttons. After its primary payload, the worm can hang the operating system and require a hard reboot. Following reboot, it hooks file associations for .bat, .com, .exe, .ht, .hta, .pif, and .scr so that launching those files reactivates the worm and reruns its payload. Some variants can prevent Windows from booting and may display the message "Windows could not start because the following file is missing."
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Malware 2003 ... Sobig Gruel Graybird
2003 ... Sobig Gruel
Email- and file-sharing-propagated Windows worm (2003) that masquerades as Microsoft/Symantec security updates, displays fake Windows Error Reporting dialogs to induce user interaction, mass-mails itself to contacts, disrupts system usability (e.g., terminates/impairs Explorer, ejects CD/DVD, opens Control Panel), and hooks multiple executable/script file types so execution re-triggers the payload; some variants can prevent Windows from booting.
Malware 2003 ... Gruel
Match every observed IP, domain, and hash against your live telemetry.
Named campaigns wielding this family, with evidence pinned to each claim.
CVEs this family uses for access and lateral movement.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Every documented technique, ranked by evidence weight.
Reddit, Mastodon, and CTI community discussion around this family.