In addition, the survey found that 15% of participants would delete files or change passwords upon exiting.
While a number of organizations have invested in technologies to help detect and defend against external attackers, many companies are starting to better understand the risks from insider threats, which a recently published whitepaper said may actually be a larger issue.
https://resiliencepost.com/2017/07/18/more-than-half-of-ex-employees-still-have-access-to-corporate-networks/
According to the report insider attacks are more difficult to detect and prevent than external ones, with 91% of respondents in a similar survey of IT and security professionals reporting they feel vulnerable to both malicious and accidental insider threats.