A security exposure in an operating system or other system software or application software component. Before the Internet became mainstream and exposed every organization in the world to every attacker on the planet, vulnerabilities surely existed, but were not as often exploited.

In light of this madness, mostly perpetrated against Microsoft, the architecture of future operating systems has changed. Designing software to be bulletproof against attacks is like building a house where every square inch is fortified with steel and sensors that detect intrusions. Patching an existing operating system written by hundreds of programmers who were not dwelling on this issue when they wrote the code is an onerous job.

Security firms maintain databases of vulnerabilities based on version number of the software. If exploited, each vulnerability can potentially compromise the system or network. For a database of common vulnerabilities and exposures, visit http://icat.nist.gov/icat.cfm. See network security scanner and vulnerability disclosure.