GootLoader Malware Uses 500–1,000 Concatenated ZIP Archives to Evade Detection
Jan 16, 2026
Malvertising / Threat Intelligence
The JavaScript (aka JScript) malware loader called GootLoader has been observed using a malformed ZIP archive that's designed to sidestep detection efforts by concatenating anywhere from 500 to 1,000 archives. "The actor creates a malformed archive as an anti-analysis technique," Expel security researcher Aaron Walton said in a report shared with The Hacker News. "That is, many unarchiving tools are not able to consistently extract it, but one critical unarchiving tool seems to work consistently and reliably: the default tool built into Windows systems." This leads to a scenario where the archive cannot be processed by tools like WinRAR or 7-Zip, and, therefore, prevents many automated workflows from analyzing the contents of the file. At the same time, it can be opened by the default Windows unarchiver, thereby ensuring that victims who fall victim to the social engineering scheme can extract and run the JavaScript malware. GootLoader is typically distrib...