An attacker used an undocumented and unknown application exploit to gain access to a file
server. Which of the following BEST describes this type of attack?

A.
Integer overflow

B.
Cross-site scripting

C.
Zero-day

D.
Session hijacking

E.
XML injection

Explanation:
The vulnerability is undocumented and unknown. This is zero day vulnerability.
A zero day vulnerability refers to a hole in software that is unknown to the vendor. This security
hole is then exploited by hackers before the vendor becomes aware and hurries to fix it—this
exploit is called a zero day attack. Uses of zero day attacks can include infiltrating malware,
spyware or allowing unwanted access to user information. The term “zero day” refers to the
unknown nature of the hole to those outside of the hackers, specifically, the developers. Once the
vulnerability becomes known, a race begins for the developer, who must protect users.