How have network firewalls evolved?

Firewalls have become ubiquitous across the enterprise IT landscape because of their proven ability to stop bad traffic from entering corporate networks and protect a company’s most valuable assets. So how have firewalls evolved over the years and what are the latest trends in firewall security?
Initial firewall designs were simple devices that inspected each piece of traffic as it entered a corporate network and either allowed it or blocked it.
Over the years firewalls have advanced to become much smarter. They now not only block known bad traffic, but they understand who each user is on the network and can grant different policies for various types of users. In a school for example, students may not be allowed to access social media sites, but teachers can.
The early 2000s saw the advent of next generation firewalls. Compared to previous firewalls, these devices pack in many more features, including deep packet inspection, anti-virus, intrusion prevention, SSL inspection and sandboxing, which is the process of testing questionable traffic to determine what impact it will have on the network.
The firewall market is healthy and growing. According to IDC, demand for security appliances grew 10% between 2015 and 2016 to become an $11.6 billion dollar market, with 2.7 million security products shipped in 2016.
Firewalls are just one important part of a comprehensive network security platform. While firewalls have advanced to become powerful tools for stopping a wide variety of nefarious traffic, the best network security defense includes an educated workforce who do not fall for phishing attacks and visiting vulnerable sites.