Firewalls
One of the strongest defense mechanisms a business owner must have. A firewall, then, is a software (or even hardware, in some cases) that filters all traffic (as being instructed to) between your computer (or network of computers, in cases of businesses) and the Internet.
Types
>>Traditional network-level firewall
The basic thing it does is that it examines packet headers, and refuses to allow packets to pass through the
firewall unless their headers match the rules—as defined by the firewall administrator or designer.
>> Application-level firewalls
Theses are the latest firewalls that use complex rules to look at the content of a packet, the type of traffic it
represents,its source or destination address,the ports involved, the application being called, and many other factors
to discover. It basically block packets that contain malicious payloads.