A vulnerability or flaw is a weakness in a computer system that allows an attacker to undermine the integrity of that system, i.e., its normal operation, confidentiality, or integrity of the data it contains.
Let's take an example, you own a beautiful home and you have placed a fairly substantial device to ensure its security. On the front of the house, you've gone all out: armored door, cameras, ... Except that at the back of the house, you forgot that there was a simple door with a padlock . This is the weakness of the security system.
A vulnerability is not a problem in and of itself, but bad people seek to exploit them. To exploit a vulnerability, one must send malicious code called a payload.
In everyday life, some people like to exploit our vulnerabilities to exert some control.
Here are some of the most well-known vulnerabilities:
- Zero Logon: flaw in Microsoft Active Directory servers
- EternalBlue: flaw in the SMB protocol (originally exploited by the NSA)
- Shellshock: flaw that impacts Linux, Unix and macOS systems
- Heartbleed: flaw that allows access to portions of a server's memory
Vulnerabilities found are described on media that must be independent of a publisher, vendor or government.
With each new discovery of vulnerabilities, it is important to update the impacted computer systems: Operating system, hardware, ...
But what is a zero-day vulnerability? It is a vulnerability that has not been published or has no known patch. As a result, it is highly prized by hackers (high market value).