GootLoader Malware Uses Malformed ZIP Archives to Evade Detection

A fresh tactic has emerged among cybercriminals using GootLoader, a JavaScript-driven malware installer. Instead of standard compression, they now distribute broken ZIP files designed to slip past digital defenses. These flawed archives exploit differences across decompression programs – some fail to process them, others do so partially. This mismatch lets malicious code stay concealed during scans yet run normally when opened by users. Findings detailed by Expel show that inconsistent parsing logic in software plays right into attacker hands. Hidden scripts activate only when handled by specific tools found on typical machines. 

Starting with a strange structure, these harmful ZIP files combine around 500 to 1,000 smaller archives into one large package. Because of this layered setup, standard programs like WinRAR or 7-Zip cannot properly read them – tools often relied on during malware checks. Due to the confusion they create, automatic detection systems frequently skip examining what’s inside. Yet, when opened through Windows’ own built-in decompression feature, the file works without issue. 

That smooth operation lets victims unknowingly unpack dangerous content.

Since 2020, GootLoader has maintained a presence among cyber threats, primarily spreading via manipulated search results and deceptive online ads. People looking for official forms or corporate paperwork may unknowingly land on hacked WordPress sites offering infected files. These corrupted archives, once opened, trigger the payload delivery mechanism e

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