A zero day is a security flaw that has not yet been patched by the vendor and can be exploited. The name evokes a scenario where an attacker has gotten the jump on a software vendor, implementing attacks that exploit the flaw before the good guys of infosec are able to respond.| CSO Online
Malware is a blanket term for viruses, worms, trojans, and other harmful computer programs hackers use to wreak destruction and gain access to sensitive information.| CSO Online