The Atlanta Journal Constitution reports that a disgruntled employee was recently sentenced to a year and a half in prison and three years of supervised release after he was found guilty for hacking his former employer, costing the company more than $800,000 in damages. While the threat of outside cyber-attacks are growing every year, inside hackers are a real and often overlooked threat as well.

Charles Taylor was a systems administrator for a lumber and building materials distributor located in Arkansas. In 2018, the company was acquired by a larger wholesaler in Atlanta. While he continued working at the company after the acquisition, he was unhappy about his new employers.

A month after leaving the company, Taylor started conducting a multistage effort to sabotage his previous employers’ network. After encrypting his network connections, Taylor changed the passwords to the network routers in dozens of warehouses, costing the company $100,000. Soon after, he hacked into the company’s central server and shut it down. This crippled the company’s communication and forced employees to take orders by hand and with personal cellphones. Over the course of a two-day period, this cost the company over $700,000 in lost profits and remediation costs.

Federal prosecutors charged 60-year-old Taylor with one count of computer fraud and was ordered to pay $834,510 in restitution.