PDFs are widely used business file format, which makes them a common target for malware attacks. Because they have so many features, hackers have learned how to hide attacks deep under the surface. On the surface, PDFs. are secure, but because they have. so many “features,” hackers have. learned how. to hide. attacks deep. under the. surface, attacks are hidden in PDFs, which are common among business file formats, Imperva says.”]