If I have a firewall do I need an antivirus.

Hello Iliton,
For sure you will need to have an antivirus on your system even though you have a firewall. A firewall is windows application that comes with it when you install the operating system and it offers protection from any attacks or threats that may want to bring down the system.
But there are some threats that the firewall may not be able to recognize as threats and they may be so dangerous when they gain access to your system. Threats like the ones that can be acquired by using infected flash drives or external drives, those that can be as a result of surfing the internet and many others. That is where you will find the antivirus to be important since it has features like link scanners for scanning every site you access on the internet and identity protection to avoid execution of any malicious software.
Therefore you strongly need an antivirus.
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Regards
Mahesh Babu