Firewalls are security systems designed to prevent unauthorised access to or from your computer or private network. Firewalls can be implemented in hardware, software or a combination of both.
Firewalls sit between the user’s computer and the external network, examining the traffic and filtering out any data that doesn’t meet a given set of criteria.
Firewall software will warn/ask the user when unknown or new software tries to access external data sources.
In short, firewalls are an essential tool in the fight to stop hackers and malware.