PDFs made up the bulk of weaponised file types because they are easily constructed and transmitted, said Barracuda Networks Inc.
According to its advisory platform Barracuda Security Insight, of the PDFs scanned in the last three months, nearly 41 million were part of an attack, with many containing links to bad sites and active scripts.
It also added that compressed files are an increasingly popular way for criminals to transmit disguised attacks.
Barracuda expected these trends to continue, with extensive use of weaponised file types to carry out massive attacks.
“Organisations often become aware of vicious cyberattacks after the damage has already been done,” said Barracuda technology senior vice president Fleming Shi, in a press statement.
Barracuda Security Insight worked by analysing large volumes of global threat intelligence from multiple sources and presented its findings in the form threat trends reports, with detailed information on attack campaigns and an aggregated threat score.
It included real-time activity seen from the following traffic: e-mails, network perimeter, web access and endpoints like malware, botnets, ad fraud and compromised dead apps.