Zero Day Home Cybersecurity Dictionary Zero Day Zero Day refers to a vulnerability in a system or software that was not previously known until after it was successfully hacked (either by a nefarious or ethical hacker). The term originated from the notion that the security community had zero days of knowledge about the vulnerability before it was exploited. This contrasts to other vulnerabilities where the security community is aware of the issue and has responded by making a patch available. Zero day exploits are far less common than exploits of known vulnerabilities, but can be especially damaging. Related TermsHackerPatchingPatch Management Share: Seeking Clarity? View the Cybersecurity Dictionary for top terms searched by your peers. Back to the Dictionary RELATED INSIGHTS BLOG February 13, 2018 Using Micro-Segmentation to Protect Your Data – Part 2 While micro-segmentation, software-defined networking (SDN) and software-defined data center (SDDC) technology providers VMWare, Cisco and Amazon Web ... See Details Read more about Using Micro-Segmentation to Protect Your Data – Part 2 How Can We Help? Let us know what you need, and we will have an Optiv professional contact you shortly.