IT security firm Webroot claimed that 97 percent of the malware encountered by its user base in 2015 was unique to a specific endpoint, which indicates that hackers are relying heavily on polymorphic software that constantly creates new variants to avoid detection.

In its just released annual Threat Brief, Webroot noted that the number of observed malware family variants skyrocketed from 14,000 in 2014 to 130,000 in 2015. Similarly, the number of observed family variants of adware, spyware and other unwanted non-malware applications jumped from 1,000 in 2014 to 90,000 in 2015.

This suggests attackers are making their code “more difficult to detect, using polymorphic distribution models and rapid new variant generation to circumvent traditional detection methods,” the report read.