An AlgoSec survey of information security professionals shows human error is to blame for network outages. 66 percent of respondents cited human error in the configuration of network devices as the most common cause of outages in the past 12 months. The most common security gateways were firewalls, installed on 98 percent of corporate networks, along with anti-virus (found on 90 percent) and content filters (on 85 percent) Firewalls were said to require the greatest investment of time and were held responsible for causing the most network disruptions.”]
Source: https://www.csoonline.com/article/2134712/humans-being–why-those-outages-are-our-fault.html