zero-day – refers to the very first time a new type of exploit or new piece of malware is discovered. At that point in time, none of the anti-virus, anti-malware or other defenses may be set-up to defend against the new form of exploit.
zero-day (or zero-hour or day zero) attack – a computer threat that attempts to manipulate the computer application vulnerabilities that are undisclosed to the software developer. Zero-day exploits is the actual code that can use a security hole to carry out an attack. These exploits are used or shared by attackers before the software developer knows about the vulnerability.
zeus – is a trojan form of malware that can be used to target and steal confidential information (such as banking information) or install ransomware. It has been around for some time (since 2007) but is subject to repeated improvements and variations. It continues to be one of the main forms of malware used in many drive-by downloads and phishing attacks. Once in place, it can operate by keylogging, man in the middle attacks and other mechanisms.
zombie — A term related to the malicious concept of a botnet. The term zombie can be used to refer to the system that is host to the malware agent of the botnet or to the malware agent itself. If the former, the zombie is the system that is blinding performing tasks based on instructions from an external and remote hacker. If the latter, the zombie is the tool that is performing malicious actions such as DoS flooding, SPAM transmission, eavesdropping on VoIP calls or falsifying DNS resolutions as one member of a botnet.