Polyglot files exploit structural compatibilities between common file formats to create a single file that can be interpreted differently by various applications. This is possible because some formats read headers from the end (e.g., ZIP), some formats are ZIP containers themselves (e.g., DOCX, APK), and some have loose structural requirements allowing partial parsing. Attackers use polyglots to bypass security filters and deliver malware via mass mailings or targeted attacks. Notable examples include PhantomPyramid malware using EXE and ZIP combined, PDF files with DOC extensions carrying malicious macros, and MSI installers appended with malicious JAR files. This technique is classified under MITRE ATT&CK as Masquerade File Type (T1036.008). The threat complicates detection and forensic analysis due to the file's dual nature.

The use of polyglot files enables attackers to evade detection by security tools that rely on file type identification, increasing the likelihood of successful delivery of malicious payloads. It can lead to phishing attacks, malware infections, and more complex incident investigations. The technique allows attackers to deceive both automated systems and end users by presenting files as benign while containing malicious content. This can result in unauthorized code execution, data compromise, and persistence within targeted environments.

No official patches are applicable as this is a technique rather than a software vulnerability. Organizations should enhance detection capabilities by using security tools capable of deep file inspection and heuristic analysis to identify polyglot files. User awareness training on the risks of opening unexpected or suspicious attachments is recommended. Incident response teams should consider polyglot files as a potential evasion method during investigations. Regular updates to email filtering and endpoint protection solutions may improve detection efficacy. There is no indication that this threat is already mitigated or requires no action.