That would depend on the environment, but fire is the common environmental threat. Hackers also threaten the environment of computers. Spies also threaten business and government environments. Firewalls are not a threat of any kind.
The greatest threat to most species is
How a community plans to respond to a given threat
I need the top ten places where earthquakes are a threat to people for tomorrow
Ozone is not a threat to humans at atmosphere. It is something which protects us from UV radiations.
Humans and human activity are the biggest threat to humans.
No, Just a online threat.
Just an online threat, unless you take the term 'firewall' literally and light up a forest. :P
fire
False
Yes.
No. Hackers are generally regarded as external human threats. Internal human threats include disgruntled employees. They may also be hackers, but the fact they are employees makes them an internal threat, not the fact they are hackers.
Hackers
hackers
Not all, some are good some are bad. White hat hackers are good, and black hat hackers are bad.
Black Hat: Criminal Hackers White Hat: Authorized Hackers Grey Hat: โJust for Funโ Hackers Script Kiddies: Ametuer Hackers Green Hat: Hackers-in-Training Blue Hat: Authorized Software Hackers Red Hat: Government-Hired Hackers State/Nation Sponsored Hackers: International Threat Prevention
Black Hat: Criminal Hackers White Hat: Authorized Hackers Grey Hat: “Just for Fun” Hackers Script Kiddies: Ametuer Hackers Green Hat: Hackers-in-Training Blue Hat: Authorized Software Hackers Red Hat: Government-Hired Hackers State/Nation Sponsored Hackers: International Threat Prevention
Hackers with concent are called ethical hackers and they are encharged with keeping the virus threat up to a minimal level.